CPD: An energy strategy that FITs the bill

Matt Dickinson, commercial director of sustainable development group BRE, explains the background to the UK Feed-in Tariff grant mechanism.

The UK’s Renewable Energy Strategy (RES) and the UK Low Carbon Transition Plan outlines the government’s 2020 vision for a low-carbon economy. The target is to achieve an 80% reduction in carbon emissions by 2050. Renewable energy from wind, water, sun and sustainable bio-energy will play a crucial role in making this vision a reality.

Feed-in tariffs have been highly successful in continental Europe at driving greater use of solar PV technology and renewable electricity generally. In many European countries, annual installation capacity increased by more than 300% in the first year after the introduction of feed-in tariffs.

After one year of operation in the UK (end of May 2011), 141MW of installed capacity was confirmed on the Feed-in Tariff scheme, covering 39,461 installations. The graph on page 38 shows the growth for individual installations since the scheme began in April 2010.

What is the Feed-in Tariff?

Feed-in tariffs (FITs) are applicable to households, businesses and, indeed, virtually any property owner.

Under the FIT scheme, electricity suppliers pay a generation tariff to independent small-scale low-carbon electricity generators as follows:

• Generation tariff — A set rate paid by the energy supplier for each unit (or kWh) of electricity generated. This rate will change each year for new entrants to the scheme (except for the first two years), but once they join they will continue on the same tariff for 20 years, or 25 years in the case of solar electricity (PV).

• Export tariff — They will receive a further 3p/kWh from their energy supplier for each unit exported back to the electricity grid, ie when it is not used on site. The export rate is the same for all technologies.

• Energy bill savings — Tenants/residents will make savings on their electricity bills because generating electricity to power their appliances offsets the electricity required from their energy supplier.

A summary of the tariff rates and key aspects of FITs is shown in the table overleaf. Because demand has been so high, with nearly 200MW (or 150 hectares) of large-scale solar farms in the planning system, the government has reduced its support for PV systems above 50kWp.

Microgeneration certification scheme (MCS)

Similar to the Gas Safe Register, the MCS licences certified installers to use an industry-recognised certification mark to promote the fact that they have met the requirements of the MCS. To gain MCS certification an installer must meet safety, quality and robustness requirements for the supply, design, installation, set-to-work and commissioning of renewable microgeneration technologies.

Installers certified by BRE Global can display the MCS certification mark combined with the BRE Global certification mark. Product certification involves type testing of products against industry-recognised international standards and an assessment of the manufacturing processes, materials, procedures and staff training.

As well as ensuring renewable installations are safe and perform as the marketing literature claims, using MCS-certified products and installers is a requirement for receiving both FIT (<50 kWp installations).

Full lists of MCS certified products and installers can be found at www.microgenerationcertification.org/

Practical issues to consider

It is worth getting accredited and independent advice on whether PV is the most suitable technology for your building. This will ensure the building is assessed in line with recognised standards and methodologies for its energy consumption, suitability of technologies, their generation capability and application and, once selected, designed appropriately. Free site surveys are available, but the advice might be biased towards a particular technology.

The following is a selection of practical issues you need to bear in mind if you are considering a PV installation:

1. Type of PV technology

PV is generally manufactured from silicon, of which there are common cell types: these being crystalline (often labelled mono, poly or multi, consists of silicon sliced from a solid ingot); and amorphous, or “thin film” (where a thin film of silicon is deposited on a backing (usually glass) from a vapour or liquid). The performance and cost will vary — crystalline generally provides a higher yield, but costs more.

2. Feasibility: design and application

The design of the system needs to consider many factors, including orientation, tilt angle, and scale of system to the application. These all have implications for system performance, but the main requirement in the UK is for array panels to face south (or at least between south-east and south-west).

For maximum collection, they should be tilted at an angle of between 20 degrees and 50 degrees from horizontal. The table on page 40 provides an indication of how output of the PV system will vary according to pitch and orientation.

3. Location

It is a common assumption that yield values will be highest for the southernmost sites (eg south-west of the UK). Although this is generally true recent field trials completed by BRE show that there are often more significant issues affecting loss in performance than geography and we have seen good performance in installations right across the UK.

4. Shading of the array

The shows a roof-integrated array with crystalline silicon roof tiles, where the left-hand side of the array is shaded by the adjoining building.

It is obvious that shading of part of the array will lead to reduced output, since the irradiation received by the PV modules is reduced. However, because of the connection arrangements of most PV arrays, the loss in output is generally larger than the geometrical area of the shading might suggest. As a result, significant losses have been observed at several field trial sites as a result of array shading.

There are two main causes of shading. First, the array can be shaded by trees (or other vegetation) that are sufficiently tall and situated close to the array. Second, another part of the building on which the array is mounted, for example a protruding roof or other items mounted on the roof (chimney, aerial, satellite dish etc).

5. Adherence and compliance with standards and regulations

The design and installation of any PV system must comply with relevant legislation such as Electricity at Work Regulations, Health and Safety at Work etc Act and other relevant standards and codes of practice. A number of important aspects need to be considered by approved electrical system designers and contractors including:

• adherence to the requirements for electrical installations BS7671 the IEE Wiring regulations;

• compliance with Construction Design and Management regulations, including working at height, manual handling of glass and eliminating the potential of live working and good installation practice;

• recommendations for the connection of small-scale embedded generators in parallel with low voltage networks (Engineering Recommendation G83/1 (2003);

• compliance with Building Regulations, including Part P (electrical safety) where prior notification must be given to local authority unless the work is carried out by competent registered persons;

• generation meters should be placed where they can be easily read and isolation switches must be located in an easily accessible position in case of emergency;

• inverters should be accessible for assessing basic system status, but often they are supplied with a remote monitoring device showing system performance. Or this information can accessed via a monitoring website.

6. Labelling not present or incorrect

Simple labelling is also very important. For example, a schematic of the installation, information allowing the owner to identify correct system operation, a simple fault identification guide and details on how to isolate both high and low voltage sides of the system are essential. In addition, if the system is not working properly, it is important that operation and maintenance manuals include as fitted drawings and commissioning certificates. These areas, together with additional criteria, are covered in greater detail within the MCS scheme.

7. Planning permission

It may not always be necessary to submit a planning application for a PV installation. The reason is because there is a general planning permission or “permitted development right” relating to microgeneration which, in certain strictly limited circumstances, may authorise a householder to install PV cells.

Permitted development rights for PV allows domestic installations unless:

• panels when installed protrude more than 200mm;

• they are to be placed on the principal elevation facing onto and visible from a highway in buildings in Conservation Areas and World Heritage Sites.

The government is currently consulting on permitted development for PV in non-domestic buildings.

8. Wind load analysis

It is important that before design is carried out the structural load analysis for modules, array bracketry and also wind loading for proposed PV array is carried out for the proposed building. Guidance on calculating the wind loading is given in BRE Digest 489 – Wind loads on roof-based photovoltaic systems. Alternatively the structural calculations and options for the support steelwork and wind load checks should be completed or verified by a qualified structural engineer.

There are several designs and quality of fixings available. While selecting the method of mounting the modules to the roof, the duration of the FIT scheme and design life of the system should be considered. It is recommended that fixings are adequately protected from corrosion for a minimum of at least 20 years as per MIS3002.

9. Supply chain partners

Selecting the right supply chain partners is very important. As well as ensuring MCS certification of product and installer you should also consider:

• design capability and professional indemnity;

• client feedback and track record;

• risks of non-performance & risk mitigation;

• what performance guarantees/warranties are offered?

• if a roof needs to be replaced and the panels are not delivering, who is liable for the consequential loss?

• what if ad hoc repairs are required to keep the panels functioning, who is liable?

• how are liabilities divided with regard to the roof, for example damage caused by installation, weatherproofing, additional upkeep?

10. Monitoring & maintenance

As PV technology has no moving parts and is silent in operation. It can be difficult to know if the system is generating efficiently unless suitable monitoring systems are in place. This can be critical with regards to FIT performance and return on investment. Therefore, it is crucial to ensure testing and commissioning has been completed in accordance with relevant standards and regulations (eg BS7671 and MCS requirements for the supply, design, installation, set to work commissioning and handover of solar photovoltaic (PV) microgeneration systems).

Ensuring a suitable monitoring regime is in place is also imperative. This may be as simple as a monitoring display on site. Alternatively, remote monitoring systems can be set up with alarms when the yield drops below expected values.

BRE runs monthly briefing events on FITs, including detailed coverage of financing options.

Visit www.bre.co.uk/fitsandrhi for more information

Additional information for this article was provided by Lee Hargreaves, associate director at WSP

Drilling down the costs

To understand the financial benefits of the FIT, consider the example of 4kWp solar PV panel installed on a home. Say the total annual electrical consumption for the home is approximately 4,500kWh a year.

The installation could generate approximately 3,360kWh a year. For every kWh unit of electricity generated, the owner of the panel receives 43.3p through the generation tariff. In addition, for every kWh generated from the technology that is also used in the home, the occupier saves up to 13p by reducing the amount of electricity bought from an energy supplier.

Electricity generated by the panel which is not used in the house cannot be stored and is therefore exported into the local electricity grid, attracting a payment of 3p per kWh through the export tariff. 

Capital costs depend on the size and type of installation. For this example, it has been assumed that the installed capital cost of a 4kW array is £15,000 for a one-off retrofit installation. Allowing for operation and maintenance costs at approximately 1% of capital costs a year, equivalent to £160 a year in this example, the net annual income would
be £979.

If no panels are installed, the annual electricity bill would be £585. This is a differential of £1,564 a year. So in simple payback terms, the investment would pay for itself in just under 10 years. 

Despite plenty of sunshine, the left side of this PV array is shaded by the adjoining buliding