Site evaluation is the key to a succesful solar PV Project. Every location is different, different roof structures, orientation, angle of roof, localised shading, horizon and of course, weather.
All of these have an impact on the effectiveness of a solar PV array and should be taken into account at the time of a survey. The Government requires that all solar PV projects are assessed in accordance with Standard Assessment Procedures which we feel are a crude estimate of solar potential.
Whilst we do comply with the requirement to provide a SAP assessment we believe that a more accurate and detailed survey is what is required by our customers and we therefore routinely provide both the SAP assessment and a much more detailed assessment of each project to enable you to compare the results of both.
Unfortunately many operators do not provide detailed surveys and rely solely on the standardised assessments which can overstate the effectiveness of a system.
So what is involved in carrying out a feasibility study?
We use tools such as Google Earth to determine your roof area and if your roof has the right orientation, i.e. it faces somewhere from south-west to south-east. If it meets the requirements the next step is a site survey.
This will entail looking at your roof structure, tile/slate, purlins/rafters etc. to decide on how a system might be mounted to your roof and to ensure that it can take the weight of a system.
While we're there we also look at the roof angle and record any other roof structures e.g. chimneys, skylights, ariels/satellite dishes etc.
2. Installation issues
While we're at your location we also take into account any installation issues; e.g. Can we get a lorry to your site? Will scaffolding be required?
3. What about shading?
Shading is a key issue for solar PV. While a panel will still generate electricity as long as it is daylight, it generates much more in direct sunlight and so shading effects can have a serious impact on the effectiveness of a system.
We look at obvious shading issues such as large trees, chimneys, gables and other buildings but also consider the effects of horizon. Horizon effects are most important for sites on north facing slopes or in valleys.
4. Location and weather data
The UK is fortunate to have been obsessed with the weather for centuries and the level of detailed records we have mean that we know fairly well what the average weather is going to be like for particular location.
We use localised weather data collected over a 30 year period to determine how much sunshine a particular site is likely to receive over the life of a solar PV system. Of course this is still a prediction so it will not be 100% accurate but it is based on long term local weather data and is the most accurate way we have of estimating sunshine at a particular location.