Solar Energy Feasibility
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 but most people are not aware of what is requried by this.
The SAP and the MCS guidelines require a proper site survey which includes an assessment of the roof structure and wind calculations.
Unfortunately many operators do not carry out detailed surveys and you should be wary of any that seem to skip over this very important part of the process.
So what is involved in carrying out a feasibility study?
1. Take a look at the roof.
We use lasers and also online tools such as Google Earth to determine your roof area and if your roof has the right orientation. As part of the survey we look 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.
The roof survey is a critical part of the process, a solar panel can weigh 20kg, so a 4kW system can weigh nearly half a tonne. If a company doesn’t bother to check your roof, ask yourself why.
2. Installation issues
While we’re at your location we also take into account any installation issues; e.g. Do you have suitable modern earthing?Can we get a lorry to your site? Where can we install the inverter, where should we run cables?
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.