 | |  | | | Solar panels on the production line at Sharp’s plant in Wrexham.
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Feed-in time
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| 12 Jan 2010
In April 2010, the government is set to introduce a Feed-in Tariff scheme that is likely to create a boom in Solar PV. Chris Laughton from The Solar Design Company explains how the scheme will be implemented and outlines some important considerations for installers.
Feed-in Tariffs (FiTs) are incentives which aim to encourage renewable energy use. They are anticipated in the UK in April 2010 and one technology that they are expected to give fresh impetus to is the generation of electricity from photovoltaic (PV) modules.
The exact details are yet to be set by government but the intention is that there will be two parts to FiTs payments:
• A fixed payment from the electricity utility for every kilowatt hour (kWh) generated (the ‘generation tariff’).
• A guaranteed minimum payment additional but lower than the generation tariff for every kWh exported to the wider electricity market (the ‘export tariff’).
This arrangement will encourage localised use of renewable electricity with the double benefit that renewable 'generators' will also be able to offset their gains against electricity that they would otherwise have bought. Different tariff rates are likely to apply dependent on the size and type of application as indicated in the
accompanying table. Where an installation is not connected to the national grid, it is called ‘stand-alone’. In the short-term it is possible to obtain grant funding as well as the expected FiT from the Low Carbon Building Program.
It was the Energy Act 2008 which first enabled the UK Government to offer financial support for small-scale electricity generation. Under the proposed UK FiT scheme, regional and national electricity utilities will be obligated to buy renewable electricity at above-market rates set by the government.
The proposed thresholds are up to a maximum limit of 5 megawatts (MW) capacity of PV modules which allowsfor huge areas greater than several football fields if desired. The aim is for PV owners to receive a guaranteed payment for generating electricity from renewable sources.
Cash backUK Secretary of State for Energy and Climate Change, Ed Miliband, has given the scheme for all the different generating technologies a new name: 'clean energy cash back'. The EU Renewable Energy Directive has set the UK an ambitious target of meeting 15% of its final energy consumption using renewable energy sources by 2020 with 2% of all UK electricity expected to be from renewable resources.
The head of the newly formed New and Renewable Energy Centre (Narec) in Northumberland, Tim Bruton, has made the claim that if every south-facing home in the United Kingdom fitted solar panels they would generate enough electricity to meet the country’s energy needs.
To take advantage of this market, it is important that you understand some background information about the technology, and we can’t emphasise enough the important role that the design and installation process will play in ensuring consumer confidence.
The story solar:
The rest of the world: Significant growth in solar power in Spain, Germany, California and Italy has been largely attributed to FiT schemes. Many of these tariffs involve fixed payments that are guaranteed in the long term: 20 years in the cases of Spain and Germany.
Initial cost: The initial cost of a PV system is significant and it is important to optimise the components and position of any system. Current capital costs for small PV systems, assuming a new-build, can be expected at around £5,200 for a 1 kWp system in 2009 on a new house. Retrofit costs are slightly higher due to costs of scaffolding and wiring, hence for a 1kWp system this becomes £6,500 and for a 2kWp system £11,000. This suggests the cost per unit of PV electricity is around £0.25/kWh assuming both a 25 year life and zero cost capital. By 2020, this cost is expected to drop below that of ordinary purchased electricity for domestic users. The skill of an installer will be in explaining to a potential customer why it makes sense, in effect, to pay for their electricity bill in advance whilst helping the environment.
Making the financial case: To put forward a strong financial case for photovoltaic FiT, it makes good business sense for electricians to partner up with designers and financiers. With interest rates so low, never has there been a better time for investors to put their low-earning capital into clean energy production. This is where commercial computer simulation programs start to become an essential tool in the decision-making process. Without these, it would be difficult to integrate the prediction of technical performance with that of the cash-flow and payback over many decades. The location of the PV modules must be taken into careful consideration, especially as shading caused by objects such as trees and buildings can result in vastly reduced system effectiveness.
Design software and simulation programmes: One of the most well-known simulation programs for PV feed-in tariff analysis is PV*SOL, which is now available with 3D shading analysis. The accuracy of any simulation depends strongly on the accuracy of the data entered into the program, and shading has a critical effect on performance. Simulation calculations will ideally take into account the influence of the module bypass diodes as well as the precise shading ratio for each module.
Performance predictions: To increase confidence in simulation results, any engineer should be prepared to reveal their assumptions for a performance prediction. The assumed climate data has particular importance to PV module efficiency in relation to both solar radiation and ambient temperatures. Most engineers now use long-term average data sets based on the last 20 years rather than risk simply using last year’s data, which may have been an unusual blip.
Where a roof becomes crowded with competing technologies and features, the more efficient solar products are likely to be prioritised in order to give the smallest footprint. Computer simulations will anticipate the best overall total energy production to displace conventional electrical sources. An on-site tool such as a solar site selector is used to anticipate any shading as an ideal accompaniment for computer simulations. Generally speaking, if both solar water heating and PVs are used on the same roof, the priority goes to the latter if this permits the avoidance of shading.
3D animated shading: The advent of 3D animated shading in photovoltaic computer simulations has greatly enhanced the design experience and set a new benchmark in the industry. With professional simulation software the solar industry can move forwards with the technological advances in equipment and provide high-quality support to design engineers. Training packages are available to assist familiarisation with these new developments. | |
 | | | Tariff rates are dependent on the size and type of application | |
 | | A schematic of a typical domestic PV array exporting surplus to the grid.
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 | | PV*SOL Expert is a 3D design tool for modelling photovoltaic system performance.
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