Everything you want to know about using Solar Energy is here!

Knowledge – as well as solar energy – is power! I'm very proud to announce the publication of not one but two new titles that I've been working on for a long time.

These distil much of my learning over this period about two essential topics that will help us fight climate change:

1. Passive Solar Architecture Pocket Reference
2. Solar Energy Pocket Reference

Get 20% off! E.g. paperback or e-book would be £20.79! Just enter code FLR40 on checkout. Order here:

• Passive Solar Architecture Pocket Reference
• Solar Energy Pocket Reference  

Passive Solar Architecture covers: the principles of passive solar building and passive house, a ten-step design and build strategy, calculating solar irradiance, factors affecting the choice of building materials, passive heating and cooling principles and techniques in different climates, the Passivhaus Standard and natural and augmented lighting and notes on technology and building occupation.

The book also includes conversion factors, standards, resources and is peppered throughout with helpful illustrations, equations, explanations, and links to further online resources.

Passive Solar Architecture is ideal for practitioners, architects, designers, consultants, planners, home builders, students and academics, and those working in development contexts.

This book is intended to act as an aide memoir, a reference supplement, a resource and an overview of the field. Rich in background detail, the book also includes at-a-glance tables and diagrams, equations and key definitions.

Solar Energy covers: solar radiation and its detailed measurement, the emissivity and absorption properties of materials, solar thermal energy collection and storage, photovoltaics (both at all scales), solar cooling, and the use of solar energy for desalination and drying.

The book also includes conversion factors, standards and constants and is peppered throughout with helpful illustrations, equations and explanations, as well as a chapter making the business case for solar power.

Solar Energy is for anyone with an interest in solar energy, including energy professionals and consultants, engineers, architects, academic researchers and students.

They will find a host of answers in this book – a practical assimilation of fundamentals, data, technologies and guidelines for application.

They're available in hardback, paperback and as ebooks.

Get 20% off! E.g. paperback or e-book would be £20.79! Just enter code FLR40 on checkout. Order here:

• Passive Solar Architecture Pocket Reference
• Solar Energy Pocket Reference  

Innovative eco-social housing neighbourhood reaches completion in Wales

A version of this article was published on The Fifth Estate on 17 May.

Glen Peters standing outside one of the two-bedroomed semi-detached houses.

The first tenants have moved into Pentre Solar, an eco-social housing neighbourhood being constructed in Glanrhyd, Wales. ('Pentre' means village in Welsh.)


Dr Glen Peters, chief executive of Western Solar, has an ambition for his company to supply 1000 homes and to work with housing associations and local authorities to provide social housing.

The South-facing front of a three bedroomed house with plenty of glazing to capture the sun's heat. Inside it falls onto a black, melamine-covered concrete floor to absorb the heat.

The North-facing rear of a three bedroomed house. The homes are clad in local larch. This is projected to last at least 25 years before it needs replacing. Much care in the detailing of the design should extend the cladding life well beyond this point.

Peters estimates the build cost is about £120 per square foot (AU$19 a square metre). This has led him to set a rental cost of the two-bedroom houses of £480 a month (AU$836), a level in line with the local 106 planning condition of no more than 80 per cent of local market rents. The three-bedroom houses are set at £620 a month (AU$1080). For the developer, this gives a 3.5-4 per cent return on investment.

A pair of two-bedroomed semi-detached houses. All the homes have solar roofs.

Local materials and labour

Costs have been kept low and as much as possible of the houses manufactured locally from local materials. In total 80 per cent of the building is manufactured locally out of local timber and 40 per cent – the airtight frames – are manufactured in a nearby factory – a converted cowshed – to be assembled on site.

Peters says the multiplier effect of the benefit to the local community for every £1000 invested is £2200, a factor of 2.2.

The timber frames are kept out of direct contact with the ground to prevent damp from rising:

A footing protected from damp on the patio.

The homes’ design builds upon the developer’s experience of a prototype house, Ty Solar:

The prototype Ty Solar (Ty is Welsh for House so the name means Solar House in English) in West Wales. In the background can be seen the first solar farm in Wales which finance the building of Ty Solar.

Ty Solar was constructed in 2010 using the profit from Peters’ solar farm, the first in Wales. It cost about £75,000 (AU$130,640) to build with a £47,000 (AU$81,870) grant from the Sustainable Development Fund.

The unit costs of the Glanrhyd houses, built on the site of a now-demolished garage, were higher than normal, mainly because of the land reclamation, provision of services and unusual weather-related costs, as well as complying with planning conditions in an area of outstanding natural beauty.

The three-bedroom homes occupy 100 square metres, the two-bed ones slightly less, but still feel spacious.

The company is focused on providing social housing as Peters believes there is a reasonable business in creating good quality affordable housing, as none of the large developers seem to interested in doing so.

While it is economic and technically feasible to build these homes, politically Peters’ route has not been easy.

”Politicians have been unduly influenced by volume building companies, and while they love the houses it has been difficult to persuade local authorities and housing associations of the benefit of backing this design, despite the fact that occupants have virtually zero energy bills. The key performance indicators imposed on housing associations are unduly skewed towards capital costs rather than tenant and community welfare,” he says.

He is hoping that when he has occupancy data to back up his case, more housing associations and councils will be interested in the model.

Zero energy bills

The timber frame houses are built according to passive house principles, though are not validated as such due the cost of doing so, versus the benefits.

Each monopitch roof sports 8kW of integrated photovoltaic panels. Over a year these generate surplus energy, providing an income from a feed-in tariff, as well as giving the occupants free electricity. Total energy demand is about 12 per cent of a conventionally built home. Beneath the solar panels is a galvanised steel sheet that laps over the timber frame.

They sit on a concrete slab, unlike the prototype, which was constructed using the box beam method with a suspended timber floor. Peters says concrete is more durable, with more thermal mass and has a lower maintenance requirement, although with a greater carbon footprint.

The windows are double, not triple-glazed, to keep costs low as Peters believes that the incremental benefit of the extra pane of glazing is cancelled by the cost in the mild local climate.

The insulation is all 27cm of recycled newsprint pumped into the cavity. This type of eco-insulation is in general the most economic and ecological. The paint is clay-based – breathable and with no off-gassing. Although more expensive per litre, it requires fewer coats on bare plaster.

The houses all come fitted out with the most efficient washing machine, condenser drier, kitchen, water-saving bathroom with occupancy sensors in areas such as toilets, internet connection, Wi-Fi and an outside socket for charging an electric vehicle. There are LED lights throughout.

All of these relatively spacious homes are provided with the most energy-efficient appliances and exceptional attention to detail.

Communal electric car

The Nissan Leaf charging outside one of the houses.

The occupants of the estate have been given a Nissan Leaf to use collectively, charged by the solar panels on the roofs.

“It’s a way of getting neighbours to cooperate with each other and eliminate the need for a second car,” Peters says.

Energy storage

The South-facing homes are generous in their space, their form determined by the maximum depth allowed by the passive heating.

The rest of the heating is provided in a surprising manner, using the best of old technology with new: solar electricity and storage heaters.

An installed storage heater; proven, old technology meeting the new.

Storage heaters contain thermally massive blocks that are heated up by an element. They then release that heat gradually over many subsequent hours.

This form of energy storage was introduced to British homes in the 1960s and ’70s on a special tariff called Economy 7. Since nuclear power stations could not be switched off, unlike other forms of electricity generation, these tariffs allowed people to use nuclear electricity at night – at a lower rate when national demand was low – to charge the storage heaters.

The problem was that by the time the heat was needed, the following evening, they were often too cool and many people subsequently removed them and installed central heating instead.

Here, the idea is to let the storage heaters be heated up during the day by the solar panels on the roof, meaning they are able to provide adequate heating through the evening and night provided that there has been average sunshine (50 per cent of a June summer’s day) during the day.

This may not be the case in the depths of winter and so the homes are also grid-connected. They export surplus energy when there is some – after the electric car and storage heaters have been topped up – and purchase it when not enough has been generated.

“Storage heaters are incredibly cheap,” Peters says, “and a well proven technology. Whereas the storage we had to start with in the prototype house – lithium-ion batteries – were designated a fire risk and we had them taken out. They are also much more expensive.”

A pair of two-bedroomed semi-detached passive solar houses.

The prototype house has been monitored and has well exceeded the predicted generation capacity, providing twice the electricity used over the year.

Peters says: “We have spent £2 million (AU$3.5m) researching and developing a sustainable timber building system that is 100 per cent British, powered by solar energy. We hope now to create 1000 homes across Wales and the UK, once the current political uncertainty is out of the way and we have won the argument on the efficacy of timber housing.”

David Thorpe is the author of a number of books on energy efficiency, sustainable building and renewable energy, including:

• The Expert Guide To Energy Management In Buildings
• The Expert Guide to Solar Technology and
• The Earthscan Expert Guide to Retrofitting Homes for Efficiency.

Find out more and buy the books here.

The cheap and reliable form of solar energy storage for homes that is already on the market

How should we store solar electricity? How about as heat? A Swedish research team is storing solar energy in liquid form, but it is still a way off being commercially available. A competing technology using molten salt is already on the market and shortlisted for a major renewable energy prize. But there is already a much cheaper and already well-proven solution now being used in a brand new context...

A shorter version of this article has appeared on The Fifth Estate.

The problem

Solar photovoltaic power it is increasingly being installed on buildings but a major challenge is that it is difficult to store so that it can be delivered when needed.

Storing solar electricity as heat is useful because the world uses more than twice as much energy in the form of heat as electricity. So for solar power to become ubiquitous, it needs to be delivered as heat more than as electricity – and round the clock.

Liquid solar energy

The solution of researchers at Chalmers University of Technology in Sweden is a chemical liquid that can tranport solar energy and then release it as heat whenever it is needed. The research, described in March’s edition of Energy & Environmental Science, describes how the team came up with a way of copying the means by which plants store solar energy – in molecules.

Transforming it into bonds between atoms in a liquid chemical makes it possible to transport it as well as store it.

“The technique means that that we can store the solar energy in chemical bonds and release the energy as heat whenever we need it,” says Professor Kasper Moth-Poulsen, who is leading the research team.

“Combining the chemical energy storage with water heating solar panels enables a conversion of more than 80 per cent of the incoming sunlight.”

The research project has come a long way since it began six years ago when the solar energy conversion efficiency was 0.01 per cent and the expensive element ruthenium played a major role in the compound.

Four years later, the system stores 1.1 per cent of the incoming sunlight as latent chemical energy – an improvement of a factor of 100, and ruthenium has been replaced by much cheaper carbon-based elements.

“We saw an opportunity to develop molecules that make the process much more efficient,” Moth-Poulsen says.

“At the same time, we are demonstrating a robust system that can sustain more than 140 energy storage and release cycles with negligible degradation.”

The process is based on the organic compound norbornadiene, which upon exposure to light converts into quadricyclane.

Hybrid panels

The rooftops of buildings can take advantage of the benefits of installing both solar water heating and photovoltaic modules.

Typical efficiencies for photovoltaic modules are now at least 20 per cent. Solar water heating systems have an efficiency of between 20-80 per cent, depending on the application, location and the required temperature.

Solar water heating systems make use of the full solar spectrum, whereas photovoltaics can only harvest a much more limited proportion.

Some companies have used this difference to design hybrid panels which contain both solar water heating and photovoltaic cells, particularly since the water can be used to stop the photovoltaic panels overheating, making them more efficient. The downside is the expense.

The Swedish researchers think that one of the potential applications for their technology, when it has become more efficient, will be a new generation of hybrid panels that utilise the heat, which can be released from the liquid storage medium.

Concept diagram for the hybrid solar panels

They say that combining solar water heating with their system allows for efficient usage of low energy photons for solar water heating combined with storage of the high-energy photons in the form of chemical energy.

Their simulations have persuaded them that these hybrid panels could be up to 80 per cent efficient. In terms of energy density they are comparable to a lithium ion battery.

The team will continue work on the technology to evaluate the potential cost and bringing it down by finding a way to mass produce the constituent chemicals, and to find a non-toxic solvent.

More than a pinch of salt

A totally different technology is from Sunamp, a British company that has developed its technology by collaborating with the University of Edinburgh School of Chemistry. It guarantees low-cost materials, exceptional long life, recyclability, safety and high energy density.

The technology has been shortlisted for the 2017 Ashden UK Awards alongside the work of the Passivhaus Trust and the Carbon Co-op, a community benefit society that helps its members to retrofit their homes.

An engineer installing the solar salt battery.

Sunamp’s form of storage uses a salt as a phase change material. This absorbs and releases thermal energy during the process of melting and solidifying respectively.

Similar technology is used on a large scale with concentrating solar thermal power stations, typically located in hot, arid deserts.

In this case it is used for storing energy from photovoltaic panels, waste process heat, or heat from heat pumps and micro CHP (combined heat and power) systems, in order to increase efficiency.

How does it work? In the case of storing solar electrical energy, an electrical element connected to the solar panels heats up the salt, thereby melting it.

The salt is kept liquid in a vacuum-insulated container. When heat is required, cold water is passed through the liquid in a heat exchanger, absorbing the heat and causing the salt to re-solidify. The heated water passes to the tap and the salt is ready to be charged again.

Sunamp’s batteries come in various sizes and can be used in series, meaning they can be used in anything from small homes to large hotels, for example. They take up much less space than a hot water tank, can store heat for longer and are more efficient.

The battery can store heat at half the weight of hot water in a tank storing the same amount of energy. Whether they are cost-effective depends upon the location and pattern of usage.

The easy solution

Tenants moving into a new passive solar mini-housing estate in Wales – Pentre Solar, Glanrhyd, near Cardigan – have roofs covered with grid-connected solar panels and zero energy bills.

The brand new passive solar homes for affordable social housing, covered in solar panels.

Dr Glen Peters, CEO of Western Solar, which is behind the development, has an ambition for his company to supply 1,000 homes and to work with housing associations and local authorities to provide sustainable, solar-powered social housing.

The occupants of the estate have been given a Nissan Leaf electric car to use collectively, charged by the solar panels on the roofs. So that's one form of storage.

But the homes' heating is provided in a surprising manner, using the best of old technology with new: solar electricity and storage heaters.

An installed storage heater in a passive solar house; proven, old technology meeting the new.

Storage heaters contain thermally massive blocks which are heated up by an element. They then release that heat gradually over many subsequent hours.

This form of energy storage was introduced to British homes in the 1960s and '70s on a special tariff called Economy 7. Since nuclear power stations could not be switched off unlike other forms of electricity generation, these tariffs allowed people to use nuclear electricity at night – at a lower rate when national demand was low – to charge the storage heaters.

The problem was that by the time the heat was needed, the following evening, they were often too cool and many people subsequently removed them and installed central heating instead.

Here, the idea is to let the storage heaters be heated up during the day by the solar panels on the roof, meaning that they are able to provide adequate heating through the evening and night provided that there has been average sunshine (50% of a June summer day) during the day.

This may not be the case in the depths of winter and so the homes are also grid-connected. They export surplus energy when there is some – after the electric car and storage heaters have been topped up – and purchase it when not enough has been generated.

"Storage heaters are incredibly cheap," says Glen, "and a well proven technology. Whereas the storage we had to start with in our prototype house – lithium ion batteries – were designated a fire risk and we had them taken out. They are also much more expensive – a couple of hundred rather than thousands of pounds."

This sounds like a solar energy storage solution that deserves far wider application. Good luck to the other technologies, but if I was looking for energy storage for a house, I know which I would choose.

David Thorpe is the author of a number of books on energy efficiency, sustainable building and renewable energy, including The Expert Guide To Energy Management In Buildings and The Expert Guide to Solar Technology and The Earthscan Expert Guide to Retrofitting Homes for Efficiency. Find out more and buy the books here.

Just two years away: cheap, easy to make, 3rd generation solar cells

In 2018, the long-promised “third generation” of solar cells will be ready to come to market. These are very different from the solar panels we see around us today. Transparent, lightweight, flexible and highly efficient, they will be able to be applied to windows, metal, polymers (as in cladding) or cement, effectively turning buildings into energy generators.

They can work in lower light conditions than current solar technologies, and don’t have to face the sun.

The technology is known as perovskite solar cells. Recently, a research team headed by Professors Michael Grätzel and Anders Hagfeldt at the Ecole Polytechnique Fédérale de Lausanne established a new world record efficiency for the cells, with a certified conversion efficiency of 21.02 per cent, increasing from 3.8 per cent in 2009, making this the fastest-advancing solar technology to date.

With low production costs, many start-up companies are promising modules on the market by 2017.

Dyesol Limited is one such company focused on commercialising these cells. Dyesol has been around for many years, longer than most of its competitors, and has secured several key patents in the field.

Three years ago it switched its research and development from dye-sensitised technology to perovskite because of its advantages.

Based in Australia, its chief executive, Richard Caldwell (above), recently released a levelised cost of energy study (which enables comparison with the market price of other energy technologies). This demonstrated costs of between 9.6 and 12 Australian cents per kilowatt-hour for the panels when manufactured and utilised at a relatively small scale. This compares to around 10-11 cents for conventional solar – about the same, but before mass production.

At the end of last year Caldwell reached an agreement with the Australian Renewable Energy Agency to receive $450,000 funding support to progress the technology towards scalable manufacture and mass commercialisation. ARENA has established a production cost of 25 cents per watt.

“The payback period for installation is a matter of a few months, as they are less energy intensive to produce than the current (usually silicon based), which take several years,” Caldwell says.

“This is extremely exciting, as it allows us to transition to a clean energy society without any subsidies from the government.

“BIPV – building-integrated photovoltaics, in other words putting solar power generation on the surface of buildings – is the holy grail of the industry and because perovskite is ultra-thin it can easily be incorporated in buildings,” he said. “But that’s longer term. We will first produce a free-standing unit for market entry, then integrated.”

The company publishes quarterly updates of progress to demonstrate progress. Caldwell says that its next landmark later this year is “the production of panels about one metre square”, with countries like Turkey partnering to produce them.

“By 2018 we hope to be in mass production of this new product.”

The first product will feature a glass substrate, allowing light through to the interior of the building. The following year, metal-printed panels will be on the market, the company says.

Australian support

Dr Richard Corkish, chief operating officer at the Australian Centre for Advanced Photovoltaics, which has been responsible for many of the improvements in silicon solar panels the world uses today, told the ABC: “Most of the important advances in solar cell work in the past has been in making incremental improvements on the same old technology that [was] invented way back in the 1950s, but [is] now much, much better.

“[Perovskite] has captured the excitement of the whole photovoltaic research community. This material might in the future offer an alternative to silicon for the main solar cell material. Our research partners – Monash University and the University of Queensland in particular – are at the forefront of this area in Australia.”

Caldwell says “the new political regime in the Australian government is more favourable to us and the Turkish government is also very supportive.”

He welcomed Bill Gates’ recognition of the technology during the Paris climate talks, when Gates joined 27 other wealthy investors to start a new investment fund called the Breakthrough Energy Coalition, to push more public and private sector funds to clean energy technology.

Gates called PSC “disruptive” and said: “When people start talking about perovskites, painted solar applications etcetera, a lot of it is down to the physics, so the majority of the money will flow through the fund.”

The technology

The most commonly studied perovskite absorber is methylammonium lead trihalide, which uses a halogen atom such as iodine, bromine or chlorine.

Unlike traditional silicon cells, which require expensive, multistep processes conducted at high temperatures (>1000 °C) in a high vacuum in special clean room facilities, the organic-inorganic perovskite material can be manufactured with simpler wet chemistry techniques in a traditional lab environment.

Methylammonium and formamidinium lead trihalides have been created using a variety of solvent techniques and vapour deposition techniques, both of which have the potential to be scaled up with relative feasibility. These techniques reduce the need to use so much polluting solvents.

Issues yet to be resolved are around stability, as the material can degrade, reducing its efficiency.

Dyesol is developing and testing this. Its most recent newsletter, published last week, announced that a test strip passed 1000 hours at 85°C with a loss of under 10 per cent. That is still a lot, so work is underway to reduce this deterioration with different types of encapsulation. To be fair, early silicon panels suffered from a similar problem.

A related challenge is cheap and environmentally friendly electricity storage, enabling solar electricity to be used also at night.

But for now, having been heralded for a long time, very cheap solar power that lets every building or object coated with it generate electricity is now within reach.

David Thorpe is the author of:

• Solar Technology: The Earthscan Expert Guide to Using Solar Energy for Heating, Cooling and Electricity


• The ‘One Planet’ Life: A Blueprint for Low Impact Development


• Energy Management in Buildings: The Earthscan Expert Guide


• Energy Management in Industry: The Earthscan Expert Guide


• Sustainable Home Refurbishment: The Earthscan Expert Guide to Retrofitting Homes for Efficiency

How to use solar energy for air-conditioning, save billions and cut emissions

Question: if you can use solar power for cooling and air conditioning then why doesn't everybody do it? After all it's a match made in heaven: just when it's so hot you need the aircon, there's lots of solar energy around.

Answer: it's fairly new, not well known and there is a relatively high upfront cost. This makes it a candidate for some sort of net metering or feed in tariffs to kickstart the market, if ever I saw one.

Yesterday I wrote about how architects can use passive solar techniques to design zero carbon buildings and/or drastically cut the need for air-conditioning in warm/hot climates.

In this article I'm going to run you through the technology principles and alternatives for active solar cooling, but first let's look at the problem.

The problem: we want to be cool

It's hot. You turn on the aircon or the fan. Your energy bill goes up

According to the NREL, "air conditioning currently consumes about 15% of the electricity generated in the United States. It is also a major contributor to peak electrical demand on hot summer days, which can lead to escalating power costs, brownouts, and rolling blackouts".

The picture is the same in Europe. For example, according to a national market survey by the Hellenic Ministry of Commerce, about 95% of air-conditioning sales in Greece occur in the period of May-August and reach about 200,000 units (primarily small-size split-type heat pumps) every year. The use of air-conditioning units in summer causes peak electric loads that periodically result in power shortages in large areas of metropolitan cities like Athens.

In southern European countries there is a well-established connection between the growth of peak power electricity demand in summer and the growth of air-conditioning sales in the small and medium-size market.

The picture is the same throughout the world whenever there is hot weather. It leads to ugly city views like this one (right).

The fact that peak cooling demand happens at the same time as high availability of solar energy offers an opportunity to exploit solar thermal technologies that can match suitable solar cooling technologies (i.e., absorption, adsorption, and desiccant cooling), cut emissions from the burning of fossil fuels and in the longer run save billions of dollars in fuel costs.

The technical solutions

Space cooling uses thermally activated cooling systems driven (or partially driven) by solar energy. The two systems are:

1. Closed-cycle:  a heat-driven heat pump that operates in a closed cycle with a working fluid pair, usually an absorbent-refrigerant such as LiBr-water and water-ammonia, or an adsorption cycle using sorption such as silica gel; two or more adsorbers are used to continuously provide chilled water;
2. Open-cycle: solar thermal energy regenerates desiccant substances such as water by drying them, thereby cooling the air. Liquid or solid dessicants are possible. a combination of dehumidification and evaporative cooling of air.

Desiccant cooling system assisted by solar energy from air collectors and PV moduls. Pompeu Fabra Library (Mataró, Spain) | Source: AIGUASOL

More case studies below the techy section, next.

Absorption NH₃/H₂O

The single stage, continuous absorption refrigeration process works as follows: The working fluid (WF), mainly ammonia and water, is boiled in the generator, which receives heat from the solar collectors at 65–80°C. Mainly ammonia, but some water leaves and is condensed at the water cooled condenser (25–35°C). The boiling working fluid in the generator has therefore to be exchanged continuously using the pump to deliver strong working fluid with a concentration of 40% ammonia, from the absorber via the working fluid heat exchanger, which heats it to 50–65°C taken from the weaker fluid leaving the generator.

The latter, now cooler, is led to the absorber, and leaves the absorber at c.35°C. Meanwhile, the condensed refrigerant ammonia has left the condenser and is injected into the evaporator by the refrigerant control valve. This works at low pressure level (2–4 bar), and the refrigerant boils and evaporates. The cold vapour flows into the absorber which absorbs it, combines it with the working fluid, and sends in back to the generator.

The thermal coefficient of performance (COP_thermal) describes the relation between the profit (cooling capacity) and the expense (heat from the collectors): COP_thermal = Q_cooling / Q_heating

Absorption H2O/LiBr

This system employs a refrigerant expanding from a condenser to an evaporator through a throttle in an absorber/desorber combination that is akin to a “thermal compressor” in a conventional vapour compression cycle. Cooling is produced through the evaporation of the refrigerant (water) at low temperature. The absorbent then absorbs the refrigerant vapour at low pressure and desorbs into the condenser at high pressure when (solar) heat is supplied. In this a single-effect absorption system liquid refrigerant leaving the condenser expands through the throttle valve into evaporator taking its heat of evaporation from the stream of chilled water and cooling it.

The vapour leaving is absorbed by an absorbent solution entering dilute in refrigerant (strong absorption capability) leaving rich in refrigerant (weak absorption capability), where it is pumped via a heat exchanger to a desorber which regenerates the solution to a strong state by applying heat from the solar-heated water stream, causing the desorption of refrigerant. It condenses in the condenser to liquid, then expands into the evaporator. The absorber and condenser are cooled by streams of cooling water to reject the heats of absorption and condensation respectively.

Adsorption

Adsorption substances are working pairs, usually water/silica gel. The solid sorbent (gel) is alternately cooled and heated to be able to adsorb and desorb the refrigerant (water). A sequence of adsorbers in deployed to use the heat from one to power another. The cycle is (refer to the schematic diagram, right): refrigerant previously adsorbed in one adsorber is driven off through the use of hot water (may be solar-heated) (right compartment).

It then condenses in the condenser and the heat of condensation is removed by cooling water. The condensate is sprayed in the evaporator and evaporates under low partial pressure, producing cooling power. The refrigerant vapour is adsorbed into the other adsorber (left) where heat is removed by cooling water.

Open cycle liquid desiccant cooling

Humidity is removed from the process air by the desiccant, which is then regenerated by heat from an available source, e.g. solar. Both solid and liquid hygroscopic materials may be used in the dehumidification of conditioned air.

Liquid desiccant systems can store cooling capacity by means of regenerated desiccant. Solar thermal energy is used whenever available to run the desorber and its associated components (hot water-to-solution heat exchanger, air-to-air recuperator, pump) to concentrate hygroscopic salt.

Later, when needed, this is used to dehumidify process air. This method of cold storage is the most compact, requires no insulation and can be applied for indefinitely long time periods.

Solid desiccant air handling unit 

Here, two air channels are mounted on top of each other. The outdoor air enters (A) where the sorption wheel with a silica gel surface dehumidifies is (B) and transfers heat from the outgoing air (C), rehumidifies it to the correct level then enters the conditioned space, increases its enthalpy by internal heat sources and moisture, and leaves as return air (G) where moisture (H and J) and heat (I) are removed as necessary and it is expelled (L).

Highly effective solar collectors should be used for the heat regeneration. The Middle European climate allows an enhancement of the adiabatic cooling mode.

Relation between the cooling capacity and the regeneration heat: COP_{thermal, plant} = Q_c,plant / Q_heat

Relation between the cooling load and the regeneration heat: COP_{thermal, build} = Q_{c, build} / Q_heat

Desiccant-Enhanced Evaporative (DEVAP) Air Conditioner

NREL, AILR Research, Inc. and Synapse Product Development have developed the DEVAP air conditioner. This consists of two stages: dehumidifier and indirect evaporative cooling.

Water is added to the tops of both; liquid desiccant is pumped through the first. Some outdoor air is mixed with return air from the building to form the supply air stream, which flows left to right through the two stages. In the dehumidifier, a membrane contains the desiccant while humidity from the supply air passes through it to the desiccant, which is also in thermal contact with a flocked, wetted surface that is cooled as outdoor air passes by it, causing the water to evaporate and indirectly cooling the desiccant.

In stage 2, the supply air passes by a water-impermeable surface that is wetted and flocked on its opposite side, providing indirect evaporative cooling. A small fraction of the cool, dry supply air is then redirected through the second-stage evaporative passages to evaporate water from the flocked surface and is then exhausted.

Evaluation

More information and a simplified evaluation tool called "Easy Solar Cooling" can help assess the cost performance of different technologies and system designs under different operating conditions. See: http://www.solair-project.eu/218.0.html

Two examples of solar cooling in practice

Video of a large scale solar cooling in South Africa:



Solar cooling in Italy

Solar cooling for a department store in Rome: The 3,000 m^{2</"600"sup> of collector area run a 700 kW chiller. Photo: Metro Cash & Carry} 

The Italian minister for economic development, Claudio Scajola, inaugurated this innovative, energy saving project in Rome on a Metro Cash & Carry building. The installation uses solar energy to cool down the wholesale outlet during summer and to heat it in winter. With its 3,000 m² of solar collectors – provided by the Italian Riello Group – this system on the store's roof is one of the biggest in Italy. It reduced the store's energy consumption by 12%, Dominique Minnaert, managing director of METRO Cash & Carry Italy, was quoted saying in the press release.

The system was designed by the British company AP Engineering Services. The chiller, with a power of 700 kW, was provided by the US-American Carrier Corporation, a leader in the areas of heating, ventilation, air conditioning and refrigeration systems. The cooling tower came from Evapco Europe, a specialist for industrial and commercial cooling equipment with headquarters in Belgium and Italy. The installation in Rome is part of Metro´s project “Energy Saving Today”. Its goal is to optimize performance of storage technology and therefore reduce energy consumption.

I fervently hope that many companies and organisations, not to mention individuals take up this exciting range of technologies.

David Thorpe is the author of 

• Solar Technology: The Earthscan Expert Guide to Using Solar Energy for Heating, Cooling and Electricity 
• Energy Management in Buildings: The Earthscan Expert Guide
• The 'One Planet' Life: A Blueprint for Low Impact Development
• Sustainable Home Refurbishment: The Earthscan Expert Guide to Retrofitting Homes for Efficiency, and
• Energy Management in Industry: The Earthscan Expert Guide

How to save millions on air conditioning by designing passively cooled buildings

Air conditioning is by far the greatest consumer of electricity in buildings in hot countries, but it needn't be so.

Architects designing buildings for regions that otherwise would require air conditioning can use passive solar techniques to keep them cool, and in many cases successfully eliminate the need for expensive air conditioning.

Right: A design for a mosque using passive solar and evaporative cooling.

Passive solar cooling operates in two stages:

1. Do your best to prevent the sun from reaching the building or gaining the interior of the building during the periods when it is in danger of overheating.
2. Then employ passive techniques to remove unwanted hot air.

Different techniques are available depending upon the climate, i.e. whether it is dry or humid.

Passive cooling for warm/hot, dry climates

Here is a summary of the techniques available for hot, dry climates with a large temperature variation from day to night use:

• high interior thermal mass;
• exterior superinsulation;
• highly-reflective OR green roofs, with insulation and a radiant barrier beneath;
• night ventilation;
• phase change materials;
• air vents;
• diode roofs;
• roof ponds;
• wind towers;
• ensure correct exterior shading on windows;
• closing windows and deploying shutters at sunrise to keep out the hot daytime air;
• direct evaporative cooling.

Above: How a wind tower on a building is used for cooling cooling.



Cooling is provided by radiant exchange with the massive walls and floor plus optional techniques explored in more detail below. Open staircases, etc. may provide stack effect ventilation, but observe all fire and smoke precautions for enclosed stairways.

Curved roofs and air vents are used in combination where dusty winds make wind towers impracticable: a hole in the apex of a domed or cylindrical roof with a protective cap over the vent directs the wind across it and provides an escape path for hot air collected at the top.

Arrangements may be made to draw air from the coolest part of the structure as replacement, to set up a continuous circulation and cool the spaces.

Passive cooling for warm/hot and humid climates

This is a summary of the techniques available for warm and humid climates, with little temperature variation from day to night:

• airtight and superinsulated construction;
• a radiant barrier beneath the roof deck;
• highly-reflective or green roofs, with insulation beneath;
• phase change materials;
• daytime cross-ventilation to maintain indoor temperatures close to outdoor temperatures.
• fresh air brought in through a dehumidifier through the crawlspace or basement by using underground pipes or use solar-powered absorption chillers;
• avoid drawing in unconditioned replacement air that is hotter or more humid than interior air;
• avoid open areas of water such as pools;
• the Passivhaus standard permits 15 kWh/m².yr of cooling energy to be used, which has proven to be sufficient in almost all cases because the Passivhaus system is highly effective in reducing unwanted heat gains;
• As above, curved roofs and air vents are used in combination where dusty winds make wind towers impracticable.

Large buildings will require detailed modelling. Power may be required for anti-stratification fans and ducts.

Shading tactics

Some tactics for providing shading to prevent the sun from reaching the building are:

• Covering of rooves and courtyards with deciduous vegetation (allowing winter access) such as creepers or grapevines permits evaporation from the leaf surfaces to reduce the temperature. At night, this temperature is even lower than the sky temperature.
• Green rooves, earthenware pots laid out on the roof, and highly-reflective surfaces (e.g. painted with titanium oxide white paint/whitewash) are all techniques practiced widely.
• Coverings that in the daytime insulate the roof but automatically withdraw at night exposing the roof to the night sky, allowing heat to leave by radiation and convection.
• Horizontal overhangs or vertical fins prevent overheating while preserving natural daylighting.
• For east and west walls and windows in summer: vertical shading and/or deciduous trees and shrubs.
• For south-facing windows: horizontal shading.
• Shutters, closed in the day.
• Highly textured walls leave a portion of their surface in shade.

Right: A summary of different shading types.

Natural ventilation

The design of natural ventilation systems varies on building type and local climate. The amount of ventilation depends on the careful design of internal zones, and the size and placing of openings.

Wind-induced ventilation is helped by siting the ridge of a building perpendicular to summer wind direction, with minimal obstruction to the wind.

In a multi-storey building, the rooms or zones on the outside faces may be separately controlled, depending upon the degree of sophistication present in the building, its size and location. If hot air is present above a set temperature, it is allowed to escape at whatever rate is necessary to preserve the comfort of this zone’s occupants, via controlled venting into a vertical space – atrium or stairwells/lift shafts – positioned centrally or on corners (with glass sides to aid the process).

At the top of this space, louvres, perhaps in clerestories or skylights, allow a controlled amount of hot air to escape, again, at whatever rate is necessary for comfort of the whole building’s occupants. Basement windows allow cool air in.

• Offset inlet and outlet windows across the room or building from each other.
• Make window openings operable by the occupants but controlled by the building management system.
• Provide ridge vents at the highest point in the roof that offers a good outlet for both buoyancy and wind-induced ventilation.
• Allow for adequate internal airflow.
• In buildings with attics, ventilate the attic space to reduce heat transfer to conditioned rooms below

It's not always possible for a building to be completely natural ventilated. In such cases fan assistance is required. Thermostats, dampers and fans would be connected to a building energy management system.

Ventilation chimneys include caps to prevent backdrafts caused by wind. These adjust according to the wind intensity and direction and increase the Venturi effect.

Turbines may be deployed to increase ventilation. Self-regulating turbine models are available. There are several styles of passive roof vents: e.g., open stack, turbine, gable, and ridge vents, which utilise wind blowing over the roof to create a Venturi effect that intensifies natural ventilation.

Bernoulli's principle

This uses wind speed differences to move air, based on the idea that the faster air moves, the lower its pressure. Outdoor air farther from the ground is less obstructed, with a higher speed, and thus lower pressure. This can help suck fresh air through the building.

Bernoulli’s principle multiplies the effectiveness of wind ventilation and is an improvement upon simple stack ventilation. However, it needs wind, whereas stack ventilation does not. In many cases, designing for one effectively designs for both.



The BedZED development in south London (above) utilises specially-designed wind cowls which have both intakes and (larger) outlets; fast rooftop winds get scooped into the buildings. The larger outlets create lower pressures to naturally suck air out.

Solar chimneys for cooling

Solar chimneys are employed where the wind cannot be relied upon to power a wind tower. The chimney's outer surface (painted black and glazed) acts as a solar collector, to heat the air within it. (It must therefore be isolated by a layer of insulation from occupied spaces.)

Pre-cooling air with ground source intakes

Right: Earth-air tunnel.

Also known as an earth-air tunnel this is a traditional feature of Islamic and Persian architecture.

It utilises pipes buried a few meters down, or underground tunnels, to cool (in summer) and to heat (in winter) the air passing through them.

They can lower or raise the outside replacement air temperature for rooms which are buffer zones between the interior and exterior temperatures.

Trombe wall effect for cooling and heating

A double skin façade is employed, the outer skin of which can be glass or PV panels. The cavity between the array and the wall possesses openings to indoors and outdoors at both high and low levels. operate more efficiently anyway).

Evaporative cooling

Evaporative cooling is used in times of low or medium humidity. As water is evaporated (undergoing a phase change to water vapour), heat is absorbed from the air, reducing its temperature. When it condenses (another phase change), energy is released, warming the air. This is the same for all phase change materials.

Right: passive solar cooling with a courtyard.

Evaporative cooling can be direct or indirect; passive or hybrid.

• Direct: the humidity of the cooled air increases because air is in contact with the evaporated water – can be applied only in places where relative humidity is very low.
• Indirect: evaporation occurs inside a heat exchanger and the humidity of the cooled air remains unchanged – used where humidity is already high.
• Passive: where evaporation occurs naturally; incoming air is allowed to pass over surfaces of still or flowing water, such as basins or fountains;
• Hybrid: where mechanical means are deployed to control evaporation.

Phase change materials (PCMs)

PCMs utilise the air temperature difference between night and day. In the daytime, incoming external air is cooled by the PCM-storage module, which absorbs and stores its heat by changing its phase state (e.g. solid to liquid).

At night-time the substance reverts to solid form, releasing its heat by being cooled by the now cooler external air. Commercially available PCMs are chosen based on the temperature of their phase change relative to that required in the space to be moderated.

Night cooling

Night ventilation, or night flushing relies upon keeping windows and other openings closed during the day but open at night to flush warm air out of the building and cool thermal mass which has heated up during the day.

It relies upon significant temperature differences between day and night time (which must be below 22°C / 71°F) and some wind movement.

The above combines edited extracts from one of my published books, Solar Technology, and a forthcoming title: Passive Solar Architecture Reference Pocketbook.

David Thorpe is the author of 

• Solar Technology: The Earthscan Expert Guide to Using Solar Energy for Heating, Cooling and Electricity 
• Energy Management in Buildings: The Earthscan Expert Guide
• The 'One Planet' Life: A Blueprint for Low Impact Development
• Sustainable Home Refurbishment: The Earthscan Expert Guide to Retrofitting Homes for Efficiency, and
• Energy Management in Industry: The Earthscan Expert Guide

How WW1 Killed a Dream of a Solar-Powered World

The world is marking the 100th anniversary of the start of World War I. This was not only the bloodiest war the world has ever seen but it saw the start of the West's involvement in carving up the Middle East and interfering in its politics for the sake of oil. We are still mired in the bloody consequences of this.

WW1 also marked the end of the world's first solar power station, which was operating only for one year, in Egypt, before the outbreak of hostilities caused it to be abandoned.

As I explain in my book Solar Technology,  a Swedish-American inventor and mechanical engineer, John Ericsson, working for the British and Americans, pursued pioneering solar work in Egypt, a British colony then, where the first parabolic trough – and the first utility scale solar technology – was developed as long ago as 1883.



John Ericsson’s design focused sunlight from a curved silvered window glass surface (called a heliostat) onto an 11-foot long iron tube central receiver to generate steam to mechanically drive a Stirling engine. The heliostat was 16 feet wide and 11 feet tall, and tracked the sun across a north–south axis. It had a maximum output of 3 horsepower (2.24kW) and was able to pump 500 gallons (2,273 litres) of water per minute.

Inspired by this, American engineer and inventor Frank Shuman commissioned the first large-scale solar power generator in Maadi, near Cairo, in 1913. Schuman dreamt of a completely solar powered world. It was theoretically possible then, as indeed it is now.

With a solar collector area of 1240m², his array powered a pump that irrigated elevated farmland with water from the River Nile.



The world's first solar power plant in Cairo 1913.

This consisted of five rows of parabolic mirrors with a total output of 88kW. This power station was more cost-effective than a similarly sized coal-based plant would have been at the time, and would have recouped its investment in four years. However, despite its success, it was only used for one year, as the First World War intervened and the Turks battled the British for control of the nearby Suez Canal.

WW1 and oil



The location of the oil fields in 1914.

This war began the worldwide predominance of oil as an energy source, as one of its causes was competition for control of the Middle Eastern oilfields. By the end of the war, British forces had secured the entire oilfields of Mesopotamia in a new League Protectorate called Iraq. This put a provisional end to any attempts of pursuing the development of solar energy on a large scale.

The British feared that the Ottomans might attack and capture the Middle East (and later Caspian) oil fields. Their Royal Navy depended upon oil from the petroleum deposits in southern Persia, which the British-controlled Anglo-Persian Oil Company owned the exclusive rights to exploit throughout the Persian Empire except in the provinces of Azerbaijan, Ghilan, Mazendaran, Asdrabad and Khorasan. To secure the oil, the British even worked with Russian Communist troops to prevent the Turkish leader Enver Pasha's goal of establishing an independent Transcaucasia.

Oil was already the lifeblood of the British Empire as the British Navy had converted from coal to oil a few years previously. British and French trucks and aircraft also ran on oil.

On November 6 1914, the day after war was declared on the Ottoman Empire, the British landed ships at Abadan, on the shores of Iraq, with a mission to protect the oilfields and make sure production was not affected. Both the French and the British had invested much money in developing these oil fields.

In March 1915 General Townsend took 30,000 troops up the Tigris to attack the Turkish army and protect the oilfields. He succeeded and continued to march onwards with the intention of attacking and capturing Baghdad. By November, 25 miles away, they battled the 25,000 Turkish army for four days. They lost, and retreated to the coast where they were beseiged for five months before 13,000 troops surrendered.

But the British hatched another plan. They captured Baghdad eventually, on March 11 1917, having marched across Palestine from the Suez Canal. The French and British sealed an agreement to share the oil and protect the oil line from Basra.

After the war, agreements were made, mostly between between France and Britain, which resulted in the carving of the old Ottoman Empire into artificial nations - Iraq, Iran, Jordan, Lebanon, Saudi Arabia, Palestine, and Syria.

The struggle is documented in the film "Blood and Oil - The Middle East in World War I" (below), which examines how this conflict laid the foundation for all the wars, coups, revolts and military interventions in the Middle East ever since, all ultimately on the need for oil.







Oil also figured in a major conflict between the Ottoman Empire and the German Empire at the strategic port of Batumi on the Black Sea and Baku on the Caspian Sea, with the arrival of German Caucasus Expedition. This was established in the formerly Russian Transcaucasia around early 1918 during the Caucasus Campaign. Its prime aim was to secure oil supplies for Germany and stabilize a nascent pro-German Democratic Republic of Georgia.

The century of conflict over oil

Oil was the black gold that motivated, and still motivates the West to constantly interfere in the Middle East, without taking into account its widely diverse population, without seeking to understand the complexity of its many cultures and ethnic composition. This is well told in William Engdahl's book `A Century of War'.

After the defeat of the Ottoman Empire, the Arab population was betrayed by the British who were their allies at the time. The British and French agreed a secret treaty to partition the Middle East between them and the British promised via the Balfour Declaration to create a Jewish homeland in Palestine.

It not until 1947 that the UK withdrew its forces from Iraq.

As long ago as the 1870s, visionary solar pioneers such as Augustin Mouchot (right) foresaw the time when the coal would run out and began to develop alternatives that could deliver the same benefits from solar power.

Mouchot, demonstrating a solar powered device that made ice at the Universal Exposition in Paris in 1878, said:

"Eventually industry will no longer find in Europe the resources to satisfy its prodigious expansion... Coal will undoubtedly be used up. What will industry do then?"

It is a great tragedy that the Earth's crust contains so much fossil fuel; not just because of global warming, but because of the millions upon millions of lives that have been lost in the wars that have been fought over access to oil in the last 100 years.

On 6 August 1882 this printing press produced copies of Le Chaleur Solaire (Solar Heat) by Augustin Mouchot, a newspaper that he created in the Tuileries Gardens, Paris, for the festival of L’Union Francaises de la Jeuenesse. It printed 500 copies an hour, using solar thermal technology.

The competition between nation states for access to these resources has time and again over the last century brought violent conflict, suffering, widespread destruction and loss of life. The presence of oil, coal and gas in a territory has been a curse as much as a blessing.

Nowadays, the phrase ‘energy security’ is being used by those who want to see local, sustainable sources of clean energy replace dirty fossil fuels. This is because the sun, wind and other renewable sources of energy are available abundantly, everywhere on the planet, with no need for conflict over their use.

Looking at the history of solar power it is clearly obvious that its development has suffered as a result of the abundance of fossil fuels. The world’s economy is currently predicated upon their use. Despite all the scientific evidence of the imminence of catastrophic climate change as a result of our continued use of these fuels, the companies and economies which rely on them are as enthusiastic as ever to exploit them.

Humanity – or its leaders – are now faced with a clear choice: whether to stick with the status quo and vested interests that aggressively promote as inevitable a continued dependence on fossil fuels; or whether to accelerate the deployment, research and development into solar and other renewable, sustainable technologies and practices.

The potential of these technologies is completely clear and proven. The scientific case for the likelihood with business-as-usual of a runaway greenhouse effect, has been conclusively established. The stakes could not be higher and the choice more stark.

British building owners can now make money by generating renewable heat

The first scheme in the world that will pay owners of domestic buildings for generating renewable heat has been launched in the UK by Energy Minister Greg Barker (seen right with MP Chloe Smith opening a 'Mr Renewables showroom' at the beginning of April).

Like feed-in tariffs for generating renewable electricity from technologies such as photovoltaic solar panels, the financial incentive scheme offers householders a fixed amount per kilowatt-hour generated from various technologies, even though the heat is only consumed in the home and not made available for others (as with home-generated electricity that is fed into the electric grid).

Called the Renewable Heat Incentive, it is based on a similar scheme for business, the public sector and non-profit organisations, that has been in operation for some time in the UK, as well as a smaller domestic scheme aimed at solid-walled, hard-to-heat homes, called the Renewable Heat Premium Payment.

Property owners apply to all schemes through the Energy Saving Trust, a government-sponsored body which promotes energy efficiency and renewable energy at the domestic scale.

The purpose of the RHI is to stimulate the renewable heat industry in the same way that feed-in tariffs have done for the solar PV industry. This has seen remarkable growth in the last four years with the cost of a typical PV system installation dropping by more than half.

The UK Government and industry body the Solar Trade Association (STA) have a target of covering over one million roofs with solar thermal and solar PV panels by the end of 2015. Over 200,000 solar thermal systems are already installed in the UK.

Global capacity for solar thermal is over 200GW - around double global installed capacity of solar power. The technology is proven and well established across Europe and elsewhere, and back in the days of previous support systems when grants were offered for installation of many types of renewable energy technologies, solar thermal was by far the most popular technology of choice for householders.

Stuart Elmes, Chair of the Solar Thermal Working Group at the STA, welcomed the launch of the RHI, saying: “Solar heating is popular with householders and quick to install, integrating easily with existing heating systems. We calculate that the returns from solar water heating are similar to those from solar power when you take into account the high price inflation for gas and heating oil.”

Paul Barwell, Chief Executive of the STA said: “With the launch of the Domestic Renewable Heat Incentive the final piece of support for household solar technologies slots into place. Together with the Green Deal for insulation improvements and the Feed-in Tariff for solar power, householders now have a great choice of Government-backed financial incentives to choose from to best suit their clean energy needs.”

Launching the scheme, the Government Minister for Energy Greg Barker (pictured right) said: "Not only will people have warmer homes and cheaper fuel bills, they will reduce their carbon emissions, and get cash payments for installing these new technologies. It opens up a market for the supply chain, engineers and installers – generating growth and supporting jobs as part of our long-term economic plan."

Technologies and payments

The technologies currently covered by the scheme are:

• Biomass heating systems, which burn fuel such as wood pellets, chips or logs to provide central heating and hot water in a home. Biomass-only boilers are designed to provide heating using a ‘wet system’ (eg through radiators) and provide hot water. Pellet stoves with integrated boilers are designed to burn only wood pellets and can heat the room they are in directly, as well as provide heat to the rest of the home using a ‘wet system’ (eg through radiators) and provide hot water.
• Ground or water source heat pumps, which extract heat from the ground or water. This heat can then be used to provide heating and/or hot water in a home.
• Air to water heat pumps, which absorb heat from the outside air. This heat can then be used to provide heating and/or hot water in a home.
• Solar thermal panels, which collect heat from the sun and use it to heat up water which is stored in a hot water cylinder. The two types of panels that are eligible are evacuated tube panels and liquid-filled flat plate panels.

Technology	Tariff
Air-source heat pumps	7.3p/kWh
Ground and water-source heat pumps	18.8p/kWh
Biomass-only boilers and biomass pellet stoves with integrated boilers	12.2p/kWh
Solar thermal panels (flat plate and evacuated tube for hot water only)	19.2 p/kWh

Only one space heating system is allowed per property but homeowners can apply for solar thermal for hot water and a space heating system.

The guaranteed payments are made quarterly over seven years for households in England, Wales and Scotland. (Northern Ireland has its own RHI scheme). The scheme is designed to bridge the gap between the cost of fossil fuel heat sources and renewable heat alternatives.
According to renewable energy expert Richard Hiblen, who has more than 14 years’ experience in this field, the RHI tariffs are ‘good for some and better for others’, but even the worst figures make the technologies more attractive than installing oil or LPG heating.

Phil Hurley, managing director, NIBE Energy Systems Ltd., a renewable heating manufacturer, called the RHI "a game changer for the renewable heating industry". He continued: “The introduction of the domestic RHI gives the industry the security and confidence it needs to realise its growth potential".

But Neil Schofield, Head of External and Governmental Affairs at boiler (furnace) manufacturer Worcester, Bosch Group, cautioned that: “the funding is weighted heavily in favour of biomass, which is one of the most expensive systems to install and one requiring the largest amount of user intervention. Questions have already been raised over whether DECC has backed the right horse in this respect."

UK Solar Strategy

Earlier this week, the UK Government also launched its Solar Strategy, which contains plans to turn the Government estate as well as factories, supermarkets and car parks in cities around the UK into “solar hubs”.

Energy Minister Greg Barker  said he believes that “there is massive potential to turn our large buildings into power stations and we must seize the opportunity this offers to boost our economy as part of our long term economic plan. Solar not only benefits the environment, it will see British job creation and deliver the clean and reliable energy supplies that the country needs at the lowest possible cost to consumers.”

The UK has an estimated 250,000 hectares of south-facing commercial rooftops, and the government believes that solar increasingly offers efficient and cost effective onsite generation opportunities to both businesses and domestic consumers.

In a further initiative, the Department for Education is working on ways to improve energy efficiency across the 22,000 schools in England, to reduce their annual energy spend of £500 million, and to encourage the deployment of PV on schools alongside promoting energy efficiency. The British Education Secretary Michael Gove said: “Solar panels are a sensible choice for schools, particularly in terms of the financial benefits they can bring. It is also a great way for pupils to engage with environmental issues and think about where energy comes from.”