Solar Photovoltaics (PV) and Solar Thermal

Solar PV – Power Generation

photovoltaic (PV) modules

Solar power generation requires PV modules which mostly come in the form of roof- or ground-mounted panels. Photovoltaic technology has come a long way since first demonstrated in the 1880s and it now approaches the point of ‘grid parity’ where a PV-generated kWh costs the same as one generated by the conventional grid mix of sources – coal, gas and nuclear. Growing supply and increasing competition amongst installers has meant costs have fallen and feed-in tariffs mean that pay back periods have fallen to below 10 years in most situations.

The factors affecting cost-effectiveness are location, shading, aspect, on site demand and feed-in tariff levels. With an almost maintenance-free life of over 20 years, PV will be the most practical renewable energy option for many. Since local energy demand and the output from the panels will seldom match, surplus electricity is sold into the grid and the income generated will offset the cost of your grid supply. Surplus energy can be stored in a battery bank for when demand exceeds PV output but the cost of this is uneconomically high, although now steadily falling.

Grid connection and planning restrictions are the main issues for large ground-mounted developments which can generate up to 200 kWs per acre. A 30 acre site near a 33kV grid connection and not over-looked may be appropriate for a feed-in tariff-eligible 5MW solar farm. Developers may pay attractive rents for such a site, perhaps £15-30,000 per year over 20 years or longer.

Solar Thermal – Water Heating

Solar water heating panelSolar water heating panels provide a reliable means of harnessing solar power. Roof panels typically heat a domestic hot water system. Installed costs are between £3,500 and £5,000 for a domestic-scale system. Dating as far back as 1911, this technology can provide almost all of your domestic hot water in summer and approximately 50% year round. Large-scale solar thermal systems can be cost-effective for commercial operations with high hot water demand, eg. milking parlours and leisure centres, pre-heating mains-temperature water to perhaps halve the water heating cost.

The pay back is long, particularly where water heating is alternatively done by mains gas or heat pump, but the Renewable Heat Incentive (RHI) can bring the payback below ten years. It is hard to place a value on the greater pleasure of the sun-heated bath!