Sunday, March 14, 2010

The cost-effectiveness of low or zero carbon energy generation

This update is following from my previous blog and George Monbiot's attack on feed-in tarriffs and responses to it.

Reliable independent figures on cost-effectiveness of low or zero carbon energy generation based on real monitored examples are yet few, and I'm trying to collate them, because this kind of evidence is what we need to help determine policy.

Crucially, page 37 of the 2009 impact assessment of the Community Energy Saving Programme (CESP) (which places an obligation on energy suppliers and electricity generators to meet a CO2 reduction target) ranks the effectiveness of non-large-scale generation measures in kgCO2 per pound sterling spent as follows:

1 Existing community heat to CHP 88 (kg CO2 score per £ spent)
2 Electric to community CHP 39
3 Wood pellet boilers (primary) 24
4 Micro Hydro (0.7kWp, 50% LF) 16
5 Ground source heat pumps 14
6 Air source heat pump 13
7 MiniCHP (revised) 9
8 Mini-wind 5 kW, 20% LF 4
9 Solar Water Heater (4m2) 4
10 Photovoltaic panels (2.5 kWp) 3
11 Micro Wind (1 kWp, 1% LF) 0

From this it is quite glaringly obvious that for both heat and power the community scale is by far the most efficient level for interventions. Right at the bottom are the single-dwelling only solutions (I dispute the figures for wood pellet boilers since data on their carbon content is disputed) except where hydro is available (not many places).

The Electricity and Gas (Carbon Emissions Reduction) Order 2008 (CERT) looked into the cost and carbon reduction effectiveness of various measures. The document Explanatory Memorandum To The Electricity And Gas (Carbon Emissions Reduction) Order 2008 contains a further Evidence Base.

In this community CHP with woodchips comes out at nine times more cost-effective in ££ per tonne of carbon saved than solar water heating and about the same as ground source heat pumps.

The figures are (- with suppliers’ cost to save one tonne C02 (£/tC02) for the Priority Group):
1 Community heating with wood chip 3
2 Ground source heat pumps 42
3 Wood chip CHP 49
4 Wood pellet boilers (primary) 58
5 Micro Hydro (0.7kWp, 50% LF) 60
6 Log burning stoves 110
7 Mini-wind 5 kW, 20% LF 125
8 Wood pellet stoves (secondary) 126
9 mCHP 176
10 Photovoltaic panels (2.5 kWp) 218
11 Solar Water Heater (4m2) 346
12 Micro Wind (1 kWp, 10% LF) 685
13 Community ground source heat pumps 697

The above underscores that renewable energies are frequently site-dependent and sensitive to economies of scale, because you have to cost the whole system.

Only 2% of UK homes can have a small wind turbine. This Energy Saving Trust report suggests the best sites and how to pick them.

Solar electricity

In my previous blog I link to actual surveys of real PV installations and the figures show that they do not generate sufficient power in the UK when we need it for the reason that there is not enough sunshine in the winter - unless you have a huge array, which is currently very expensive.

If PVs could become as cheap as a low-e coated window unit, with spray-on or printed nano-scale circuitry or similar it might be worthwhile. This is a technological advance not a deployment advance. They would also need to capture a greater range of frequencies of light.

I would suggest that the standard for measuring and marketing the rated output of a panel or a system is changed to make it more realistic and easier for buyers to understand. As discussed in the blog above, the test conditions are way different from European field conditions and led to unreal expectations, or to potential obfuscation by the industry/ unscrupulous installation companies.


All of this suggests that while renewable heat can work on a community level, only CHP can universally provide electricity, whatever the power source, and then not that much in relation to demand since there is a limit to the available waste, waste heat and biomass.

Therefore we have to conclude that for renewable electricity generation larger scale wind and marine power are what is required at a massive scale. Of these, only wind is currently cost-effective and that is why it is being aggressively pursued offshore and onshore.


Steve (energy savings through solar window film) said...

Great blog.

I stumbled across an energy source that seems too good to be true.

What is your take on it? Can it really work?

DavidKThorpe said...

No it can't. You can't get energy from nowhere. This is grid-powered. A con, basically.

Anonymous said...

When there`s no wind blowing,electricity has to come from another source and a power station can`t just be switched on but has to be kept operational ie at low efficiency so large scale wind power dosen`t replace existing power generation but merely adds to it thus expending more energy. True or false?

DavidKThorpe said...

The topic - grid integration of renewables and variability - has been extensively investigated.

One conclusion - from the UK Government report quoted below - is: "For penetrations of intermittent renewables up to 20% of electricity supply, additional system balancing reserves due to short term (hourly) fluctuations in wind generation amount to about 5-10% of installed wind capacity."

This is one of a number of myths surrounding the integration of renewables, especially wind energy, into an electricity network because of the variablility of the resource.

Peter Freere, formerly an engineering professor at Monash University in Australia says:

"It is correct that in normal electric grids (without energy storage - eg pumped storage, charging electric cars, etc.), a single wind farm would not work well on its own and some conventional energy sources are also required.

"The same applies to the conventional energy sources, especially nuclear, whose response time is so slow that they must have a fast responding generation system in parallel.

"It is also true that due to the large sizes of modern generators in conventional systems (eg. 500 MW per generator), to allow for maintenance and breakdowns, it is necessary to have a complete spare generator ready to take over when another stops working (for whatever reason)."

"Hence the risk with wind farms is not so great - no more than many conventional systems."

The largest study on grid integration was done in Germany by DENA. The gist is that investment in the grid will be necessary to integrate the new renewable generation needed meet the German target of 20% of supply from renewable energy by 2020. The investment required is less expensive than additional grid expansion if new central-station plants are built, and this investment will result in making the grid more stable with or without the renewable generation.

A March 2006 UK Energy Research Centre report analysed the results of 200 studies on the grid integration of intermittent renewables. A separate post outlines the results (Have exceeded limit of length in a reply).

Anonymous said...

Incredibly (and like Monbiot and Goodall) you've fallen for the 2010 snapshot analysis of renewables costs and completely missed the point of the PV and other feed-in tariffs, which is to drive economies of scale and reduced costs over a relatively short period of time. The PV Feed-in tariffs are reduced year on year until they will be worth less than the cost of the grid supplied alternative - please look at the PV tariffs to 2020.

If we only support the cheapest technologies at today's prices, we'd have no offshore wind, no wave and tidal power, no PV, no biomass, no anaerobic digestion, no small hydro and no small wind - because they all need far higher subsidies than largescale wind and hydro.

DavidKThorpe said...

And you're missing my main point. I repeat, it's not about scalability of current technology in mass-production. It's a technological advance. If PVs could become as cheap as a low-e coated window unit, with spray-on or printed nano-scale circuitry or similar it might be worthwhile. this is a different technology to the current panels which are not valuen for money in terms of carbon saved when you need it in the winter in the UK. Just work out how great an area of PV you would need to power a home (say 2kW) in the winter with currently on sale panels. They would need to capture a far greater range of frequencies of light and therefore solar energy per square metre for example to fit on a domestic roof.

Then there is the cost of the inverters in each house - if you don't have a separate DC supply for all your DC loads like laptops, iPods and phone chargers. And of course each time you convert from DC to AC and back to DC you lose energy and so need a greater area of panels.

Economies of scale, cutting the 'overheads' of the system, like controls and inverters, would lead you to have a much larger surface area of panels, say, maybe a whole street - maximising surface area by perhaps covering the windows with a transparent PV layer (a technology not yet at commercial development stage) and the roof with solar tiles - feeding into one inverter and one set of controls. But of course the roof and wall must be facing the right way and not be overshadowed during the whole day.

What are the real, independently monitored figures for Germany (not the industry version)?