Energy Policy: The effect of Feed in Tariffs on Solar PV take-up in the UK.

Abstract

Incentive schemes have been introduced in a number of countries to try and reduce carbon emissions, both by increasing efficiencies and stimulating demand for renewable technologies on a large and small scale. This paper briefly outlines these policies in the UK, and identifies Feed-in Tariffs (FiTs) as the policy that has led to the largest increase in PV uptake.

The factors that influence FiT design are analysed and comparisons between the UK policy and other FiT mechanisms drawn in order to highlight the dangers of inappropriate tariff levels.

The impact that FiTs have had, particularly the level to which FiTs have increased the uptake of solar PV compared to other technologies, is outlined. The appropriateness of solar PV in the UK is examined, with particular reference to large scale installations.

In the light of recently announced changes to the tariffs and the introduction of the Renewable Heat Incentive, an assessment of the likely impact on the renewables and PV market is made.

In conclusion, the elements of FiTs that encourage renewable uptake on a broad scale are outlined, and recommendations to ensure that FiTs assist in meeting renewable targets are made.

UK Policy Background

In response to the need to tackle climate change, the UK has developed a number of policies aimed at emissions reductions and renewable energy generation at both a large and small scale.

Since 1990, the UK has had a delivery programme for renewable electricity generation and emission reduction in the form of the Non Fossil Fuels Order (NFFO). Although originally designed to encourage the purchase of state-owned nuclear power in a newly privatised electricity market, the NFFO was extended before implementation to include renewable sources. The system obliged energy suppliers to purchase from generators at a guaranteed price per kWh, and was funded primarily by the Fossil Fuel Levy.

The Fossil Fuel Levy was replaced with the Climate Change Levy in 2001, acting as a tax on all non-domestic energy use, with some exceptions by sector. Businesses can enter into Climate Change Agreements in order to reduce their taxes by reducing carbon emissions.

The Energy Efficiency Commitment (2001) requires energy suppliers to deliver energy efficiency improvements such as insulation in households, as a means of contributing towards national emissions-reduction targets and the Government’s Fuel Poverty Strategy. The latest phase of the Energy Efficiency Commitment has been renamed the Carbon Emissions Reduction Target and includes micro-generation and behavioural measures within the scheme.

In 2002, the NFFO was replaced by the Renewables Obligation, which obliged suppliers to source a specified and increasing proportion of their supply from renewable sources through the purchase and trading of Renewables Obligation Certificates (ROCs), with the number of ROCs awarded for generation dependent on the renewable technology employed. Any supply that cannot be met by these sources means suppliers have to pay into a buy-out fund which is then returned to the producers in proportion to the number of ROCs presented.

2006 saw the Climate Change and Sustainability Energy Act (CCSEA) and the Micro-generation Strategy, aimed at encouraging micro-generation and the use of heat from renewables. The CCSEA made provisions for the development of a system for suppliers to buy back energy from micro-generators. The Micro-generation strategy aimed to make access to ROCs easier and to promote community projects, as the Renewables Obligation did not encourage energy production at this scale.

The 2006 Low Carbon Buildings Programme provided capital grants for small scale renewables as well as larger scale projects for public buildings and businesses. The programme ran with a significant supply shortfall. Demand was so high that in its second phase it was limited to public-sector organizations and charities and the programme has now closed.

The Energy White Paper of 2007 outlined the UK’s international and domestic energy strategies, with a further focus on renewables and micro-generation, including stated aims of improving ease of connection to the grid for distributed and micro-generators, and a focus on reducing the carbon impact of heating. The legislative aspects of this were implemented in the Energy Act 2008.

The Climate Change Act (2008) aims to enable the UK to become a low-carbon economy by setting emission reduction targets of 80% by 2050, compared to 1990 levels, and gives ministers powers to introduce measures necessary for these targets.

The EU Renewables Directive (2009/28/EC) set further legally binding targets for member states, and in 2009, the Renewables Obligation was reviewed and changed in order to further increase the flexibility of the UK energy market, and increase ease of connection.

Also in 2009, the Government published The UK Renewable Energy Strategy and The UK Low Carbon Industrial Strategy, which aimed to show how the UK can produce 15% of its energy from renewable sources by 2020, and detailing how the UK would meet its commitment to carbon emissions.

The introduction of Feed-in Tariffs (FiTs) in 2010 was a result of the powers introduced in the Energy Act 2008. This is specifically aimed at micro-generation, and provides for a guaranteed and index-linked price for any electricity produced from renewables, based on the technology type and its power output. It is ultimately funded by electricity consumers through their bills.

The principles of FiTs are to be extended with the introduction of the Renewable Heat Initiative in 2011. This will aim to increase the use of renewable heat and will be aimed primarily at large industrial and commercial users in the first phase, with domestic users accepted in the second phase, from 2012. Unlike FiTs, this will be funded from Government spending, rather than a levy on fossil fuels for heating.

The Impact of Feed-in Tariffs

At the end of 2007, it was estimated that there were a total of 2,993 solar PV systems up to 50kWe installed in the UK, with a total generating capacity of 10.3MW, largely due to the LCBP[1]. The total increase in installed capacity in 2009 was 10MW[2]. As will be shown, these figures have been dwarfed by the recent increases due to FiTs.

Table 1 - Feed-in Tariff prices in March 2012[3]

Technology Type	Capacity	Price (p/kWh)
Anaerobic digestion	≤500kW	12.1
Anaerobic digestion	>500kW	9.4
Hydro	≤15 kW	20.9
Hydro	>15 - 100kW	18.7
Hydro	>100kW - 2MW	11.5
Hydro	>2MW - 5MW	4.7
Micro-CHP	<2 kW	10.5
Solar PV	≤4 kW new	37.8
Solar PV	≤4 kW retrofit	43.3
Solar PV	>4-10kW	37.8
Solar PV	>10 - 100kW	32.9
Solar PV	>100kW - 5MW	30.7
Solar PV	Standalone	30.7
Wind	≤1.5kW	36.2
Wind	>1.5 - 15kW	28
Wind	>15 - 100kW	25.3
Wind	>100 - 500kW	19.7
Wind	>500kW - 1.5MW	9.9
Wind	>1.5MW - 5MW	4.7
Existing generators transferred from RO		9.4

As can be seen from Table 1, by far the best tariffs available are for photovoltaics, and in particular for retrofit PV with a capacity of 4kW or less. Figures released by OFGEM[4] show a total of 26,333 new installations in the period from 1 April 2010 to 31 March 2011. Of these, the vast majority, 25,571 are PV installations, with 24,641 of them being within the highest tariff bracket.

The overall PV take-up by installation type and installation size is shown in Figure 2.

Figure 2 – Number of photovoltaic installations registered for FiTs by Installation type and size

The installed capacity of these small systems is also significant, amounting to a total of 63.8 MW of a total of 77.2 MW of total PV installations as shown in Figure 3, and an overall capacity from all technologies of 94.5 MW.

Figure 3 – Total installed PV capacity through FiTs in kW by installation size

FiTs can therefore be seen to have proved remarkably successful at promoting PV uptake, and the UK was - though still comparatively small - one of the highest growth PV markets in 2011 as shown in Table 4.

Table 4 - Photovoltaic Installations in the World's Major Solar Markets (in Megawatts)[5]

Country	2010	2011	% Change
Czech Republic	1331	350	26%
France	520	550	106%
Japan	950	1100	116%
South Korea	145	170	117%
Belgium	390	488	125%
Italy	2850	3900	137%
Spain	250	345	138%
Germany	6727	9400	140%
China	400	700	175%
Greece	120	235	196%
USA	937	2073	221%
Rest of world	798	1779	223%
Ontario (Canada)	213	730	343%
Bulgaria	20	70	350%
United Kingdom	95	350	368%

However, as noted, and illustrated in Figure 5, this uptake accounts for over 97% of all FiTs installations, and is seemingly at the expense of other renewable technologies. This is hardly surprising, given that PV has the highest tariff. A study which has shown that electricity unitary price ranks second highest in order of importance for the Internal Rate of Return of a PV system, with only initial investment being higher. Actual annual electricity yield is lower in the order, followed by investment subsidy and loan interest[6].

Figure 5 - FiTs Installations by technology type and sector

This, then, leads to two questions. Firstly, how should a FiT policy be designed? What aims should it have and what factors does it need to take into account in order to provide an economical and sustainable increase in renewable uptake of all kinds? How can it contribute effectively to meeting emissions targets?

Secondly, is PV the most suitable technology for the UK in terms of carbon emission reductions or large scale investment? In that the FiT is providing such a boost to one technology, what barriers need to be overcome to encourage similarly rapid take-up in other technologies?

What makes a good FiT policy?
As green energy policy has evolved, the consensus is that obligations certificates and feed-in-tariffs are successful at spurring growth in the renewables sector. There is debate over which mechanism is better for producing environmental and economic returns. Some research indicates that certificates are better at reducing overall emissions, as FiTs do not address the challenges faced with high consumption of energy[7].  

However, a combination of tradable certificates schemes like the Renewables Obligation, which are aimed at larger power generators, and FiTs, aimed at domestic and community producers, is recognised as being the most beneficial path for rapid uptake of renewable technologies[8].

The ideas behind Feed-in Tariffs and Renewables Obligations were first used in the United States under the Public Utility Regulatory Policies Act of 1978 (PURPA), which obliged electricity companies to purchase electrical power production from small producers at a guaranteed rate.

The aims of Feed-in Tariff schemes generally include a decrease in emissions, the nurturing of new industries, energy security, and associated economic benefits[9]. The degree of emphasis placed on these goals influences the way the FiTs scheme works. The main criteria of a ‘good’ FiT policy is that it avoids windfall profits for producers and provides a stable investment framework to enable new and emerging technologies to reach ‘grid-parity’ - the stage where the costs of electricity are the same for conventional methods and the new technology[10].

Grid-parity has already been reached for PV systems in Spain and it is forecast that it will be reached in most regions of the world in this decade[11]. However Spain also provides an example of how high FiT rates can lead to inappropriate investments, as a number of installed systems, put in place rapidly in order to make the most of tariff levels, were not properly engineered, resulting in them going out of service[12]. A disproportionately high tariff level in the UK could lead to a similar situation.

Similarly, the US’s PURPA legislation had high tariffs and was widely criticised for leading to a rise in so-called ‘PURPA machines’, poorly performing generation schemes that could survive financially only due to the high tariffs paid, at the expense of consumers[13].

Economically, a policy based on obligations or incentives must be clear in terms of pricing of tariffs, and provide a long-term guarantee to ensure investor confidence, maintaining stable conditions for compliance. This encourages investment in technologies at all levels and creates a long-term and sustainable market, as a firm base in the design and commissioning of systems of all sizes is necessary, with an increasingly large and skilled workforce installing them.

The benefits to land-owners are evident. Agricultural land is particularly valuable in this regard, having large amounts of space available for renewable energy generation using most technologies.  Power generation can be simultaneous with traditional agricultural use; wind turbines are too tall to affect agricultural activities, anaerobic digesters use agricultural wastes and by-products to produce electricity and fertilisers, and even PV farms can still accommodate small livestock for non-intensive grazing[14].

The Renewable Heat Incentive

The Renewable Heat Incentive, announced in March, is an important addition to the incentives portfolio, as it broadens the range of renewable technologies, as well as the demands they satisfy. It is the first scheme of its kind, and so it will be interesting to see how it develops as a model for other countries to implement.

The main difference between the RHI and FiTs is the method of funding, however, and it may be that the RHI’s reliance on government funds may lead to a lack of resource or a need to restructure the tariffs in due course.

Nevertheless, given the large amount of energy in the UK devoted to heating, the RHI is a welcome move towards tackling a primary cause of UK emissions. It should also lead to more of a focus on system efficiency, for example by focusing market attention on CHPs for the production of electricity and useable heat, as these will be eligible for both FiTs and RHI tariffs[15]. When used for both needs, these systems can deliver an energy conversion efficiency of 75%[16].

Potential additions to FiTs

In order for a FiT to meet its aims of emission reductions, efforts to ensure that the most efficient technologies are adopted need to be included. The UK’s FiT policy works primarily on technology and power output, however different tariff levels could be set for particularly appropriate technologies.

It would be interesting, but out of the scope of this paper, to investigate the notion of FiTs based on system efficiency. For large projects, it should encourage a more thorough analysis of the system, instead of simply encouraging a ‘bigger is better’ approach. On the domestic scale, providing higher tariffs for higher generation and lower consumption could have the effect of simultaneously encouraging renewables uptake and demand reduction.

Recent Tariff Changes

A recent announcement[17] has proposed a change in the tariff rates for PV installations of 50kW and over, and the introduction of new bands, as outlined in Table 6, below.

Table 6 - Proposed changes to UK Feed-in Tariffs

Technology Type	Capacity	Price (p/kWh)	Proposed changes
Anaerobic digestion	≤500kW	12.1	<250 kW @ 14.0
			250-500kW @ 13.0
Solar PV	>10 - 100kW	32.9	50kW-150kW @ 19.0
Solar PV	>100kW - 5MW	30.7	150kW - 250kW @ 15.0
			250kW - 5MW @ 8.5
Solar PV	Standalone	30.7	≤5MW @ 8.5

This should ensure that large developments are more efficient, reducing the risk of failure or bad investments, and has the stated aim of stopping large scale commercial developers from ‘cashing in’, which was an unforeseen outcome when the FiT was originally designed[18]. It should also free up investment potential for more efficient energy projects, as it seems to have made a number of planned projects unviable, including PV on a number of government-owned properties[19] .

The announcements have caused a great deal of debate, with opponents of the changes claiming that it damages investor confidence and that the market for PV will suffer as a result[20]. Doubtless regular changing of tariff levels would cause a great deal of uncertainty, however this change is aimed at one particular type of installation and is as such a one-off change to close a potentially damaging loop-hole. In that the vast majority of the FiT uptake has been for small systems, which will be unaffected by the changes, and require a proportionately larger amount of labour, it seems unlikely that the PV industry as a whole will suffer greatly.

Other critics state that the reductions in PV prices that would result from large scale farms will now not materialise. PV prices are currently dropping at a rate of 5-8% per year,[21] however this is due to a number of factors, not solely demand, and shortages in raw materials and currency fluctuations can mean that lower prices do not necessarily materialise at the point of use[22]. Furthermore, even if mass uptake through solar farms were to lead to a reduction in costs for PV, these savings would not necessarily be passed on to consumers. A study that analysed the impact of the Low Carbon Buildings Programme on the UK PV market found no significant reduction in end-user costs, claiming that the savings were absorbed by the installation companies[23].

Is solar PV an appropriate technology for the UK?

It is generally acknowledged that for renewables to provide any significant portion of energy demand in the UK, a wide range of technologies need to be encouraged with parallel increases in efficiency to reduce demand. Of the technologies available, solar PV should certainly play a part, as the UK, though northerly, is still sunny enough to make PV viable both economically and in terms of energy payback. Furthermore it is well suited to urban situations, being both silent and emission-free at the point of use[24]. Nevertheless, the economic and energy payback is longer for PV as levels of available sunlight fall[25]. A brief look at some of the other renewable options for the UK shows where more emphasis could be placed.

Solar Thermal

A study has shown that in terms of total carbon emission reduction costs, solar thermal technologies are far better suited to the UK, with building integrated PV costing £196/tonne of CO2 avoided, solar thermal costing £65/tonne and community solar thermal costing even less at £38/tonne[26]. Solar thermal is similarly well suited to urban situations, and directly meets the demand for space and water heating, which is the largest consumer of energy in the UK[27].

The introduction of the Renewable Heat Incentive in summer 2011 should see an increase in all renewable heating systems, and it is likely that tariff levels will influence which technologies receive most attention. The RHI is going to target large industrial and commercial users in the first instance with the second phase being open to householders from October 2012[28].

Wind

The UK is recognized as having one of the highest wind resources in Europe, and wind power is cheaper than PV, costing roughly a tenth of the amount to install[29]. Although uptake has been considerable over the last few years, as shown in Figure 7, factors such as local planning constraints and vocal opposition groups have impacted on the degree of wind penetration[30]. Also notable on the graph below is the lack of any significant contribution from PV.

Figure 7 - Growth in Electricity Generation from Renewables[31]

Wales has a particularly high proportion of wind planning application refusals compared to the other regions in the UK, showing only a 10% approval rate, compared to 90 and above in Scotland and Northern Ireland and about 60% in England, with a high proportion held up in the planning process[32]. The recommendations in Technical Advice Note 8: Renewable Energy (2005) by the Welsh Assembly Government should address some of these issues by providing clear planning guidelines for renewable energy, and outlining the benefits of wind power for communities, and to meet emissions targets[33].

There are an increasing number of wind turbines suitable for urban situations, notably vertical axis turbines, which perform better in turbulent and low wind speed areas. The slower rotational speed and blade design in these turbines also makes them much quieter than horizontal axis designs, which could further improve urban electrical generation potential. Market penetration and awareness of these technologies would be key to securing a larger uptake of urban wind generation potential.

Anaerobic Digestion

Anaerobic digestion has received little attention through FiTs, with only 2 new projects in the last year. Anaerobic digestion is widely seen as best practice for dealing with a range of organic wastes, and is especially beneficial as, in capturing the methane generated by the breakdown of organic material, it prevents its release into the environment and allows it to be combusted in a controlled manner in order to generate electricity and heat.

The main drawback with AD, however, is the large capital cost and the specialist knowledge required to design a facility, as each waste stream requires different treatment. It remains to be seen whether the modest increase in tariff for AD systems will encourage more uptake for this technology.

Appropriate Solar PV in the UK

In all, solar PV - although having a role to play - should not be seen as the only answer in the quest for renewable energy sources. To a degree, FiTs has introduced a gold-rush mentality, with a number of companies offering free installations so as to reap the long-term rewards of the FiT[34].

A number of very large PV plants in the region of 5MW have been planned, using brownfield sites near residential areas, or farmers’ fields. Although the current level of tariffs may make these viable economically, it is questionable whether this is a good use of the financial resource available, not to mention the amount of space that would be occupied for 25 years or more.  A solar farm generating 5MW would require an area of around 25 acres, and would generate less than a third of the power of an equivalent system in Spain.[35]

Nevertheless, large scale projects on otherwise disused roof space, such as industrial units, could be effective, particularly if the energy is used close to source. In order to improve efficiency, industrial users could use the DC current directly[36], and thus avoid the losses incurred by current conversion and grid distribution[37]. Another issue with current conversion and large solar farms is that inverters typically work best at between 10 and 20% of their maximum load[38]. With the highly variable nature of solar energy, it is likely that the inefficiencies of a mismatched inverter would become more apparent in a large solar farm.

The degree to which PV has been marketed as a panacea is evidenced by a conversation between the author and a friend who has no mains gas connection and uses an immersion heater for hot water and heating. She was offered a 4kW solar PV system and led to believe that this would help with her particular needs. In this case, a wood or biomass boiler would be more appropriate. Although with the level of tariff she would still probably make a good return from her investment, the PV system would make a negligible contribution towards her overall energy consumption and carbon footprint, as well as costing a large amount of money that would be better spent on directly tackling her heating requirements. Again, the introduction of the RHI should address these kinds of issues to enable consumers to significantly reduce their carbon emissions as well as providing an economic return. Indeed, initial documentation suggests that it will focus on exactly these kinds of customers who are off the gas grid[39].

Conclusion and Recommendations

In light of the criteria for a good FiT, the UK’s example seems to have shown great successes in terms of PV uptake. However, as discussed, it seems that the high level of tariff for one generating technology has led to the danger of the widespread implementation of PURPA machines in the form of inefficient solar farms.

For market-based mechanisms like FiTs to be successful, the market must be able to make projections with certainty. However, it must also be steered towards the most appropriate technologies to satisfy environmental obligations, with tariffs that stimulate the economy in the long term. Market awareness of all generating technologies and a good balance between them needs to be encouraged, in order to prevent a disproportionate focus on ‘holy grail’ technologies.

Unscheduled adjustment of tariff levels should be discouraged, unless it is to counter potentially inefficient uses of resources. The proposed changes to feed-in tariff levels in the UK will have a negative impact on investor confidence for large scale solar farms. However increased emphasis on more suitable technologies for the British climate should have a greater effect on carbon emissions, and FiTs should continue to assist in the uptake of PV and all renewables in an appropriate fashion.  

Further refinements of FiTs could target appropriate large-scale PV and urban wind power, which has received little attention. Small scale PV should not be affected by the review, and the increase in uptake should continue with the current level of tariff. In particular, the RHI is a welcome addition to the incentives portfolio.

It remains to be seen whether the lack of ‘easy money’ for solar PV will encourage venture capitalists to brave the planning process for wind. Anaerobic digestion should see a small increase in FiTs in the summer however, and an increase in generation tariffs here may provide a stimulus to the large venture capitalists that would be required for AD systems, providing a more appropriate avenue for large investments. The ability of CHPs to claim both RHI and FiTs tariffs should also encourage implementation of these technologies. This is particularly welcome as they provide much higher efficiency over-all.

An investigation into the potential for an efficiency-based tariff would be interesting, and this could promote generation schemes that operate effectively, rather than simply providing high tariffs for particular technologies. By encouraging renewable generation in conjunction with energy saving, users would be encouraged to simultaneously reduce demand, thus assisting with national targets for both emissions reduction and increased renewable supply, while large installations would ensure that they are likely to be efficient before they are constructed.

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[1] Element Energy (2008), Numbers of microgeneration units installed in England, Wales, Scotland, and Northern Ireland, BERR 2008.

[2] PricewaterhouseCoopers  (2010), On the brink of a bright future? Insights into the UK solar photovoltaic market, PWC.

[3] Feed-in Tariffs Ltd (2011), Feed-in Tariffs: Tariff Levels Table, Feed-in Tariffs Ltd (online) available at: http://www.fitariffs.co.uk/eligible/levels/ (accessed 12 April 2011)

[4] OFGEM (2011), Feed-in Tariff Installation Report 31 March 2011: Excel Spreadsheet, OFGEM 2011 available online at: http://www.ofgem.gov.uk/Sustainability/Environment/fits/Documents1/Feed-in%20Tariff%20Installation%20Report%2031%20March%202011.xls (accessed 11 April 2011)

[5]Table adapted from: H. Wicht (2011) Photovoltaic Market in Europe to Account for 70 Percent of World Total in 2011, IHS iSuppli (online) available at: http://www.isuppli.com/Photovoltaics/MarketWatch/Pages/Photovoltaic-Market-in-Europe-to-Account-for-70-Percent-of-World-Total-in-2011.aspx (accessed 13 April 2011) 

[6] D. L. Talavera et al (2010), The internal rate of return of photovoltaic grid-connected systems: A comprehensive sensitivity analysis, Renewable Energy 35.

[7] M.M. Tamás et al (2010), Feed-in tariff and tradable green certificate in oligopoly, Energy Policy 38.

[8] K. H. Solangi et al (2011) A review on global solar energy policy, Renewable and Sustainable Energy Reviews 15.

[9] J. Twidell (2010) Powering the Green Economy – the feed-in tariff handbook, by M. Mendonca et al. Reviwed in:  Energy 35, 2010

[10] Miguel Mendonça and David Jacobs (2009), Feed-in Tariffs Go Global: Policy in Practice, Renewable Energy World

[11] Ch. Breyer and A. Gerlach (2010), Global Overview On Grid-Parity Event Dynamics, Q.Cells (online) available at: http://www.q-cells.com/medien/presse/publikationen/downloads/6CV.4.11_Breyer_GlobalGrid-Parity_poster_25thPVSEC_final.pdf (accessed 13 April 2011)

[12] J. Tippett (2011) The Impact of Policy on Solar Market, Solar UK (online) available at: http://www.solaruk.net/news/solarenergy.asp?item=2125 (accessed 12 April 2011)

[13] J. A. Lesser and X. Su (2008), Design of an economically efficient feed-in tariff structure for renewable energy development, Energy Policy 36

[14]The Green Company () Solar Farm Environmental Impact (online) available at: http://www.the-green-company.com/solar_farm_environmental_impact.html (accessed 13 April 2011)

[15] Ibid, p32

[16] Ibid, p43

[17] C. Huhne (2011), Feed-in Tariffs: Written Ministerial Statement by Chris Huhne, Secretary of State for Energy and Climate Change, DECC 2011

[18] ibid

[19] W. Nichols (2011), Feed-in tariff cuts result in scrapping of government's own solar project, The Guardian (online) available at: http://www.guardian.co.uk/environment/2011/apr/06/solar-power-fit (accessed 7 April 2011)

[20] E. Hughes (2011), IMS Research questions the future of solar in the UK, Solar Power Portal UK (online) available at: http://www.solarpowerportal.co.uk/news/ims_research_questions_the_future_of_solar_in_the_uk5478/ (accessed 12 April 2011)

[21] E. Goossens (2011), Solar Costs May Already Rival Coal, Spurring Boom in Panel Installations, Bloomberg (online) available at: http://www.bloomberg.com/news/2011-04-05/solar-energy-costs-may-already-rival-coal-spurring-installation-boom.html (accessed 11 April 2011)

[22] S. Wilkinson (2010), Comment: Are solar PV module prices really falling? Renewable Energy Focus (online) available at: http://www.renewableenergyfocus.com/view/11692/comment-are-solar-pv-module-prices-really-falling/ (accessed 11 April 2011)

[23] C. N. Jardine and N. Bergman (),The Status of the Uk Domestic Pv Market – A Review of the Impact of the Low Carbon Buildings Programme, Environmental Change Institute.

[24] A. Stafford and S. Irvine (2009), UK Photovoltaic Solar Energy Road Map, CESR.

[25] A. Stoppato, Life cycle assessment of photovoltaic electricity generation, Energy, Vol 33 Issue 2.

[26] B. Croxford and K. Scott (2006), Can PV or Solar Thermal Systems Be Cost Effective? In: R. Campbell-Howe and R. Campbell-Howe (eds.) Solar 2006: renewable energy, key to climate recovery, American Solar Energy Society

[27] Ibid.

[28] DECC (2011),  Renewable Heat Incentive (RHI) Scheme, DECC (online) available at: http://www.decc.gov.uk/en/content/cms/what_we_do/uk_supply/energy_mix/renewable/policy/incentive/incentive.aspx (accessed 12 April 2011)

[29] FoE (2008), Wind Power: 20 Myths Blown Away, Friends of the Earth (online) available at: http://www.foe.co.uk/resource/briefings/wind_myths.pdf (accessed 12 April 2011)

[30] D. Toke et al (2006), Wind power deployment outcomes: How can we account for the differences? Renewable and Sustainable Energy Reviews 12.

[31] DECC (2009),  Electricity Growth, DECC (online) available at: https://restats.decc.gov.uk/cms/electricity-growth/ (accessed 12 April 2011)

[32] C Tomlinson (2009), An Analysis of Onshore Wind Delivery and Planning Performance, BWEA 28 Conference Proceedings (online) available at: http://www.bwea.com/28/proceedings/index.html

[33] WAG (2005), Technical Advice Note 8: Planning for Renewable Energy, WAG (online) available at: http://wales.gov.uk/desh/publications/planning/technicaladvicenotes/tan8/tan8main1e.pdf?lang=en (accessed 11 April 2011)

[34] Energy Saving Trust (2011) Consumer guidance on free solar PV offers, EST (online) available at: http://www.energysavingtrust.org.uk/Generate-your-own-energy/Solar-electricity/Consumer-guidance-on-free-solar-PV-offers (accessed 13 April 2011)

[35] B. Webster (2011), Countryside to sprout solar farms as firms cash in on subsidy scheme, The Times (online) available at: http://www.timesonline.co.uk/tol/news/environment/article7125779.ece (accessed 13 April 2011)

[36] S. Mekhilef et al (2011) A review on solar energy use in industries, Renewable and Sustainable Energy Reviews 15.

[37] E. Cetin et al (2010) A micro-DC power distribution system for a residential application energized by photovoltaic–wind/fuel cell hybrid energy systems, Energy and Buildings 42.

[38] C. Demoulias (2010) A new simple analytical method for calculating the optimum inverter size in

grid-connected PV plants, Electric Power Systems research 80.

[39] DECC (2011), Renewable Heat Incentive, DECC p6