This site uses cookies. By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy.
Skip to the content

IOP A community website from IOP Publishing

Powered by Movable Type 4.34-en

Renew your energy: November 2011 Archives

Desert solar race

| | TrackBacks (0)

Deserts get a lot of sunlight and there is currently something of a race to develop and deploy the best technology to exploit this free energy.

Concentrating Solar Power (CSP) systems with mirrors, dishes or parabolic troughs focussing the sunlight to raise steam to run a turbines are currently in the lead. There have been some major developments in Spain and the USA, but also now in N Africa and the Middle East, with new projects opening in Morocco (the 470 MW Ain Beni Mathar hybrid project) and Egypt (the 150 MW Kuraymat hybrid project). And more are planned. For example, the UAE is planning a 100MW project, and the Egyptian National Plan for 2012 -17 includes a 100MW CSP plant in South Egypt, while the follow-up National Plan for 2018-2022 has 2,550 MW of CSP. The German-led Desertec project seeks to build on the CSP option, making supergrid links back to the EU. It has plans for a €600m 150MW CSP plant in Morocco as a first stage.

It's hard to know what the impact of the recent political convulsions in North Africa may be, but CSP does seem likely to continue to move ahead in the region, as well as elsewhere- the largest CSP array so far planned is the 1 GW Blythe project, being developed in California by Solar Millennium LLC, on which more later.

A solar industry roadmap, as outlined in a study by A.T. Kearney and the European Solar Thermal Electricity Association, ESTELA, sees solar thermal reaching 12 GW of installed capacity globally by 2015, 30 GW by 2020 and between 60 and 100 GW by 2025. But that may prove to be pessimistic- CSP is not just limited to desert areas. For example, South Africa has a plan for a 5GW solar park, with the initial 1000MW phase, aimed for 2012, incorporating an already planned Eskom 100 MW CSP plant, which has received part funding from the World Bank. The Indian Ministry of New & Renewable Energy's National Solar Mission aims to generate 20GW of grid linked solar power by 2022, 50% CSP. And in Australia a new 'Zero Carbon Australia 2020' report has 42.5 GW of CSP supplying 60% of total electricity there by 2020!

However a rival technology - Concentrating Photo Voltaic (CPV) power - may challenge CSP. CPV uses conventional solar cells but with large arrays and sunlight focussing arrangements, as with CSP. The crucial point is that mirrors are cheaper than solar cells. There are already some very large projects in existence, 20 MW or more globally, including the 4MW array in Springerville Arizona, and the 10MW Masdar project in the UAE. And costs are falling- some say faster than for CSP.

A GTM Research study claims that the growing market for CSP is being seriously challenged by the rapidly falling price of solar photovoltaics. GTM predicted that, although the CSP market will grow by around US$7 billion over the next two years, it will then tail off, due to the dramatic decrease in the cost of solar PV panels. So although CSP project costs are set to decline between 3% and 7% per year from 2010 to 2020, PV costs will also continue their own substantial declines, with PV expected to maintain a cost advantage (on both a cost-per-watt and cost-per-kWh basis).

In fact, some utility companies are already choosing PV over CSP for future solar plants. For example, Masdar, the Abu Dhabi government backed renewables company, had been backing CSP. Its $600m, 100 MW Shams 1 CSP unit should be completed in 2012. But the newly proposed 100MW Noor solar PV plant will cost less than Shams 1, because of improving efficiency and "the normal learning curve for the industry," according to Frank Wouters, director of Masdar Power.

The cost battle is also evidently having an impact in the USA. According to an report carried by Renewable Energy World, conventional residential rooftop solar PV system in Los Angeles can deliver lower electricity at less cost per kilowatt-hour than the most cost effective, utility- scale concentrating solar power plant. It noted that CSP had higher operations costs and a higher cost of capital than for the residential rooftop system, and there were also transmission infrastructure and efficiency losses, which would increase the cost of power from the CSP plant further.

It may be too early to make longer-term policies on the basis of calculations like this, but PV and CSP do seem to be rivals. CSP has the major advantage of being able to store heat in molten salt heat stores, so that power production can be continued after the sun goes down, while most PV cell performance falls with time and rising temperature. But then CSP plants have to have some form of cooling as with any steam raising system- air cooling is less efficient than water cooling, but one thing deserts don't have is water, so it would have to be piped in, adding to the cost. And with cell cost falling, PV may increasingly have the edge. After all, its not just domestic roof top PV systems or simply arrays that are in contention, new ideas for very large-scale CPV systems, including energy storage, are also emerging

Earthscans 'Energy from the Desert' three-volume book set edited By Kosuke Kurokawa et al , details the background and concept of Very Large Scale Photovoltaics (VLS-PC). Overall the authors are very optimistic- they say VLS-PV can be competitive with fossil fuel-fired plants assuming economic energy storage is available- they look to Vanadium flow batteries. And longer term they see large scale PV solar are becoming a dominant energy option.

CSP and CPV both have similar environmental impacts in terms of their land use footprint, with some projects in the USA falling foul of local concerns about desert wildlife, and CSP's need for water.

But there should be plenty of desert areas around the world where there are minimal land use conflicts, and some North African CSP projects have been seen as being used partly for desalination- with sea water piped in over perhaps long distances from the Mediterranean, possibly linked to Solar greenhouses projects.

New ideas may also emerge. It's conceivable that CSP and CPV or PV arrays could be combined. There are some small-scale hybrid solar thermal-PV systems for domestic uses, the big advantage being that the solar heat absorbers keep the PV cells cooler, so they operate more efficiently, in tandem, with heat collectors in wafers in a sandwich with PV cells. Although it's harder to see how this could be achieved with large scale focussing systems, it could be worth exploring in hot desert environments.

Hybrid CSP/PV systems were mentioned as a future option by the developer of the 1GW Blythe solar project in California mentioned earlier. Reflecting the changing fortunes of CSP and PV, it has now decided that the first 500-MW phase will be switched from CSP to PV technology because they say market conditions in the US now favour PV. But they also noted that CSP was a valuable 'grid-stabilizing renewable energy source with storage capabilities,' so a combination might prove to be the best option.

For more: Peter van der Vleuten, Free Energy International:

Since their output is variable, wind turbines have to be backed up, usually by fossil fuel plants, so some say that the carbon savings from having wind power on the grid are undermined. This issue has been the subject of sometimes heated debated for some time.

Back in 2008, the House of Lords Select Committee on Economic Affairs report on 'The Economics of Renewable Energy' referred to an argument made to the Committee by a witness from the Renewable Energy Foundation (Campbell Dunford) who claimed that any carbon savings from wind power were offset by the need to run conventional (and flexible) fossil fuel plant at part load to balance the fluctuations in wind output (e.g. to balance supply and demand when the wind is blowing less). Part loading means that the backup plants are run inefficiently, so producing more CO2 per kWh of output than they otherwise would.

Based on other inputs to their review, the Committee disagreed with this argument. They concluded that 'The need to part-load conventional plant to balance the fluctuations in wind output does not have a significant impact on the net carbon savings from wind generation'.

In its response to the Select Committee, the government agreed with this statement and estimated the net saving from raising the share of renewable electricity to 32% to be about 45-50 million tonnes of carbon dioxide-- about 8-9% of total CO2 emissions--after taking account of the cost of part- loading plant.

Certainly it is usually argued that the extra cost of fuel/ and the extra CO2 produced is only of the order of 2-3%. The issue is explored in Godfrey Boyle's 'Renewable Energy and the Grid: The Challenge of Variability' (Earthscan, 2007).

However, some critics point to new real time data from the USA and elsewhere, which they claim indicates otherwise:

For example, one analysis of recent US data suggests emission savings from wind plant are as low as 0.1 tons of CO2/MWh in California, compared to an average figure for the US as a whole of 0.6 and a figure of 0.8 attributed to the American Wind Energy Association.

But it rather depends on what fuel is being displaced. In California it's mostly (low carbon) gas and (zero carbon) hydro, whereas in the Mid West it's mostly (high carbon) coal- so the figure there is 1ton/Mwh saved.

The carbon saving benefits from wind are also undermined in the US by the fact that, when wind availability is high, much of the potential output from wind projects has to be curtailed- i.e. not used. This is mainly due to there being weak grid links, which are unable to take it all and distribute it to where it is needed. The same thing has happened recently in Scotland. Having large inflexible 'must run' nuclear power plants on the grid also doesn't help.

Better grid links can clearly help reduce the need for wind curtailment, so of course could electricity storage, which will also help when wind availability is low, although energy storage is expensive (see my earlier Blogs). Interactive load management to reduce (or shift) demand peaks can help reduce the need for back up when there is less wind available, so can imports of energy from wind generators elsewhere, where it is more windy, via a long distance supergrid, balanced by exports when wind is available and demand locally is low. See

So there could be solutions, and they may not add too much extra cost. Certainly the recent European Wind Integration Study, produced by the European Transmission System Operators, says the benefits of wind energy in terms of fuel and CO2 saving greatly exceed grid balancing and reinforcement costs, put at 0.21-0.26 p/kWh and 0.4p/kWh respectively, for 181 GW of wind; and extra grid reinforcement could reduce the former to 0.17p/kWh.

And beyond that, the EWEA Tradewind study and Greenpeace's various [R]evolution reports suggested that pan-EU supergrids could offer major benefits in terms of reducing the impact of local variability- for example perhaps doubling wind power's capacity credit. and

However perhaps inevitably not every one agrees. For example , Pöyry's North European Wind and Solar Intermittency Study (NEWSIS) has found that 'The creation of an offshore 'super grid' and a major upgrade of energy interconnections are not the silver bullet solutions to Europe's energy needs'.

It says that the introduction of improved connectivity would only partially alleviate the volatility of increased renewable energy generation. Basically it claims that wind and solar output will be highly variable and will not 'average out', even over wide areas- it looks at the NW of Europe- and concludes that 'heavy reinforcement of interconnection doesn't appear to offset the need for very much backup plant'. So it claims that 'inter-connectors are not a complete solution'. Pöyry study summary: www.poyry. com/linked/en/press/NEWSIS.pdf

Actually no one has said that inter-connectors were 'a complete solution'- there would also be a need for backup, storage, and demand side management and so on. Moreover, unlike the earlier EWEA 'Tradewind' study and Greenpeace reports, which looked across the whole of Europe, Pöyry only looked at the North West. Assuming a wider footprint- including the sunny south, and the windy east, and possibly also North Africa, then the situation would be very different- as has been explored in Gregor Czich's seminal study 'Scenarios for a Future Electricity Supply', now published by the IET.

However the debate on wind balancing continues, with some inputs being quite dramatic. For example, a study of the influence of wind energy on the CO2 output of fossil-fired generation of electricity in Ireland claims that, in absence of hydro buffer storage, the CO2 production of the conventional generators increases with wind energy penetration, and that the reduction of CO2 emissions is at most 'a few percent', if gas fired generation is used for balancing a 30% share of wind energy.

Even if only partly true, it looks like a good case for a supergrid link- Ireland's grid is too small.

A recent input to the debate is a new EU "Offshore Grid" project analysis, co-financed by the European Commission, which looks at the benefits of building a meshed European grid offshore, which it says will significantly increase security of electricity supply across the EU.

The House of Commons Select Committee on Energy and Climate Change has also recently backed the supergrid: the IET had told the Committee, a supergrid could provide a much wider range of opportunities to export excess electricity when the wind is blowing and new routes to import electricity at times of low-supply.

Supergrids are not the only or complete answer to variability, but along with other measures, they should be able to help. For an extensive, authoritative, report on the variability issue see the IEA's 'Harnessing -Variable Renewables.'

The German Advisory Council on the Environment (SRU) has produced a very detailed report setting out pathways for a transition to renewable electricity. It concludes that is possible to get to 100% by 2050, as against the current German government target of only 80% by then.

The SRU comments 'In our view, the prospects for this transition are far brighter than the government would have us believe; and we are far less persuaded than the government appears to be concerning the compatibility of nuclear power and renewables. But many of the recommendations and concepts in the present report are relevant regardless of whether the goal is to achieve 80 or 100% renewable electricity'.

However, rather than going it alone, it suggest that an alliance with Denmark and Norway could be the best arrangement for generation, grid balancing and storage, for example integrating in the regions hydro for pumped storage. That was seen as possibly preferable to reliance on importing power (e.g. from Concentrating Solar Power projects) from North Africa.

Some of the scenarios rely heavily on wind power, both offshore and on-land, and also on solar photovoltaics (PV), which, on one scenario, make up a large proportion of the 2050 mix (with around 100GW of PV installed by then). However SRU claims that this is not the only option and that if demand could be reduced from 700TWh by 2050 to 500TWh, then much less PV would be needed.

It sees this as a preferable option and is critical of the way PV has been supported so far in Germany, arguing that it was expanding too rapidly and imposing unsustainable costs. The current high rate of expansion 'would result in half the capacity that is needed for a wholly renewable electricity supply in 2050 in the high electricity demand scenarios to be already installed in 2020. This means that unnecessary capacity would be installed prematurely, which in turn would increase long-term renewable electricity costs and jeopardise acceptance of a wholly renewable electricity supply'. Consequently, it says that 'Photovoltaic support should be drastically reduced so as to rectify mismanagement in this domain, whose current expansion rate far exceeds that deemed necessary'.

Exit from PV?

Why the change of heart on PV? Germany has been at the forefront of PV with around 19GW now in place. That, SRU says, is the problem- it's boomed too fast, partly due to cost reductions, so that the high FiT tariffs impose too much cost on consumers. This same argument has been heard across the EU- in Spain, Italy, France, and now in the UK, all of whom, like Germany, have imposed Feed In Tariff (FiT) cut backs or capacity caps for PV. The latest German cuts range from 3-15%. Some see this as just a failure of political nerve- they say we should leave FITs alone, since PV prices will then fall, as the market builds, and the cost pass through to consumers can also then be reduced.

SRU evidently doesn't agree and also has more fundamental problems with PV. While they note that some think PV 'will be competitive once grid parity is achieved, with solar electricity generation costs on a par with household electricity rates, they say that 'this assumption fails to reckon with the fact that household electricity demand and solar energy production are highly asynchronous. Households with solar panels need to be able to draw energy from the grid at times, which would significantly reduce the economic benefit of home PV installations in the (likely) event that some household electricity needs to be drawn from the grid during high rate periods. Hence the achievement of electricity generation costs that can compete with the prices charged by power companies by no means indicates that photovoltaics deserve a place in the future energy mix'.

Some might see throwing PV out of the mix as an odd idea. Economically it's almost certain to get very much cheaper. And SRU's technical case against PV is not that strong- PV can make a lot of sense for day-time occupancy buildings, for summer air-conditioning and for topping up night time storage heaters. More generally, although load factors are low, we are going to have to get used to balancing variable supplies, as we have more renewables on the grid. SRU may be right that PV will make it harder, but it's a huge resource well suited to access via roof tops, easy to install and run-with no moving parts to go wrong. It may have been unwise to try to use FiTs to get its initial very high price down rapidly, but that doesn't means the technology is rubbish. Or that FiTs are no use, if well designed, with effective price degression mechanisms.

However, it is true that, in the worsening economic climate, the FiT for PV have been seen as provocatively high and hard to defend. SRU says that further support in Germany is 'no longer justifiable on the grounds of learning curve effects, for the market for PV installations has grown considerably and is now international in scope. Even if Germany stopped promoting photovoltaic energy, the remaining PV installation market would be large enough to allow for further cost reductions'. So, in effect, SRU is saying that, although it has cost a lot, the FiT has done its job and no more support is needed. More pragmatically they say that since the national alternative energy programme cost apportionment 'cannot be increased without meeting political opposition, perpetuating the current photovoltaic support framework would deprive renewables of funding that have the capacity to produce electricity far more efficiently'.

In fact through, SRU doesn't suggest abandoning PV entirely. They say that 'in the interest of political credibility and preserving the relevant technical skills and know-how, PV capacity expansion should not be discontinued altogether'. Instead it suggests that 'the scope of PV expansion should be kept at a low level that however still ensures that installed capacity can be adjusted to potential changes in demand. Only if a rise in electricity demand appears highly probable, PV capacity expansion should be promoted accordingly.'

So PV should in effect be kept in reserve. SRU says 'The planning period for such a capacity expansion - which ideally would be realised as late as possible -should be keyed to the relationship between the capacity needed and the possible annual expansion rate.' It adds 'If projections of large decreases in PV installation manufacturing costs are accurate, this would be yet another reason to rein in photovoltaic energy support. The later PV installations are installed the lower their social cost will be'.

Some might see SRUs conclusion that 'PV support urgently needs to be reined in' as a capitulation to right-wing free-market enthusiasts, equally it might be seen as a sensible recognition of the limits of PV and FiTs in the current context. Most observer now agree that FiT tariff levels for PV need cutting, but the debate over how much continues- in the UK, focusing on the proposed very drastic 50% cut, with the resistance campaign's slogan being 'Cut don't Kill'.

More PV solar cuts

| | TrackBacks (0)

The full Department of Energy and Climate Change (DECC) review of the 'Clean Energy Cashback' Feed In Tariff (FiT) for photovoltaic (PV) solar installations resulted in further cuts to support - following on from the 72% cut in the tariff for PV projects over 50kW that had emerged from the earlier 'fast track' review.

The new cuts were prefigured in a speech at the end of October by Energy Minister Greg Barker, who, while welcoming the successful installation so far of over 100,000 PV arrays (around 300MW), said: 'Much of the growth in PV has been as much about consumers accessing the Government backed tariff as accessing the technology. High net worth individuals chasing returns which are now easily reaching double figures at a time when interest rates for savers have collapsed to an historic low. That can't be right.'

So DECC is planning to more than halve feed in tariff incentives for solar PV projects of 4kW or less from, in effect, December this year- reducing the tariff from 43p/kWh to 21p/kWh, which it says should yield a 4.5% rate of return. They also proposed reductions to the tariffs for PV installations between 4kW and 250kW, 'to ensure those schemes receive a consistent rate of return'.

There's also a proposal to introduce an energy efficiency requirement for FITs for solar PV. If the building does not meet the energy efficiency criteria the installation would receive a lower FIT rate of 9p/kWh. In addition there's a proposal for new multi-installation tariff rates, set at 80% of the standard tariffs for individual installations, for 'aggregated' PV schemes- where an individual or organisation gets FIT payments from more than one PV installation, located on different sites, as in 'rent a roof' schemes.

Launching a consultation on the proposals, Barker said that the existing tariffs led to 'returns for investors in solar PV that are simply not sustainable and, without action, could result in the spending envelope for the scheme rapidly being breached' He explained that 'If the Government took no action, by 2014-15 FITs for solar PV would be costing consumers £980m a year, adding around £26 (2010 prices) to annual domestic electricity bills in 2020. Our proposals will restrict FITs PV costs to between £250-280 m in 2014-15, reducing the impacts of FITs expenditure on PV on domestic electricity bills by around £23 (2010 prices) in 2020.'

DECC is to publish a separate consultation 'around the end of 2011' on 'other aspects of the scheme including the tariffs for other FIT technologies. As part of its review of the FITs, DECC will also consider 'whether more could be done to enable genuine community projects to be able to fully benefit from FITs.'


In a fact sheet it evidently released prematurely, the Energy Saving Trust gave an early warning of the scale of the cuts and said that under the proposed changes payback time would be 18 years for a 2.9kW system, eight years longer than at the current levels. But it said that the new rate of return, which it put 4%, was more "appropriate" than the original 5-8% rate, due to the changes in the investment market that has seen interest rates slashed.

Dave Sowden of the Micropower Council agreed that 'they needed to recalibrate it....but if you go below five per cent then you completely wipe out free solar and social housing schemes. It just becomes a rich man's game.' Friends of the Earth concurred: 'The proposals will pretty much exclude everyone who does not own their own home and have significant savings to hand from installing solar'. The proposal to backdate the changes to December also caused concern - e.g. it could impact on those half way through installation negotiations. Overall, the timing of the cuts was a big problem for developers.

However, the idea of linking supply schemes to efficiency was widely seen as making sense- it's foolish not to sort building energy losses out first. Barker had said he wanted a new 'whole-house approach', including new measures to ensure that all new domestic solar PV sites meet minimum energy-efficiency standards: 'It cannot be right to encourage consumers to rush to install what are still expensive electricity-generating systems in their homes before they have thoroughly explored all of the sensible options for reducing their energy consumption first. Frankly, such a standard should have been a pre-requisite for accessing the FiT subsidy from day one'.

He also, maybe sensibly, urged developers to move into the solar thermal market, which has seen slower deployment rates under the pilot Renewable Heat Premium Payment Scheme than those experienced by the PV under the FiT. While that may be an option for some developers, there were predictions of massive job losses in the PV sector, and a lot of resentment about the cuts. Surely if the FiT system was allowed to work, the cost would reduce as the market built, with FiT prices being 'degressed' continually, so consumers wouldn't be hit hard.

The DECC report suggests otherwise- PV had boomed too fast. The consultation report notes that, as at September 2011 ' 255MW of solar PV had been registered for FITs. This compares to the 94MW that was originally projected for this point in time', driven mainly by 'the reduction in the cost of PV systems'. Barker claimed that 'The cost of an average domestic PV installation has fallen by at least 30% since the start of the scheme - from around £13,000 in April 2010 to £9,000 now'. In addition, DECC noted, there were increased returns available from solar PV due to the '13% increase in retail electricity prices since April 2010, which has increased the savings from avoided consumption of imported electricity'. It added that multiple installation schemes had also played role in the uptake of FITs.

All of this threatened to push the cost passed on to consumers up rapidly- although that has to be put in perspective- DECCs impact report indicates that, at present, the FiT added just £1.40 p.a. to typical household bills. But what about the benefits, not just the cost savings for those on the scheme, but the climate benefits, which all share, and the indirect cost saving since less fuel has to be used nationally?

More specifically, there were social benefits. As DECC admitted, some multiple installations schemes enabled 'those who cannot afford the upfront capital costs of purchasing a PV installation, including the fuel poor, to share in some of the benefits', as in 'free solar', rent a roof schemes.

However DECC noted that some felt that for these, 'the principal beneficiaries are generally the third parties rather than the hosts of the generating equipment.' DECC say that 'the returns available to such schemes are higher than in the case of individual installations. We therefore consider there is a strong case for adopting a different approach and tariff for multi-site generators of FITs'.

So it's cuts across the board. It may be true that the UK FiTs were quite generous to PV. But then the FiT system was a new venture for the UK. DECC says that the new PV Tariffs are now similar to those in Germany. That's not quite true. Despite recent cuts, most of the German tariffs are still larger, and the German FiTs have been running for many years, so that PV has a well-developed market. Here it is still in its infancy. And now it could stay that way.

DECCs consultation report is at: