Photovoltaics

Looking at the example of 50-250kWp systems - not large PV farms, where different rules apply,   a250kW peak array as per the image to the left could generate 270kWh of renewable electricity over the course of a year in a typical UK application.   

The installed cost of the PV array as of February 2018 is around £900-£1,000 per kWpeak installed.  However one should consider - depending on where the installation is - that roof access and reinforcement, marking out of walkways, and mansafe systems may be required, increasing costs.  

Also don't forget that PV's collect air born pollution (e.g leaves, pollen and sap, road dust, bird dropping) so requiring cleaning, and that the panels and inverters that convert DC power from the PV panels to usable AC power have a degradation profile & finite life and also need maintenance.  

When feed-in-tarriffs started initially, the intent was to incentivise end users to take up the new technology and so back in 2010 was circa 32p/kWh.  This gave a payback of about 2 years. Since then electricity prices have escalated by about 50% but feed-in-tarriffs have dropped to 1.7p/kWh.  This has pushed paybacks out to c 7-8 years. 

Permission needs to be sought from the district network operator to connect such generating assets onto their networks.  All will require G59 equipment to be fitted that shuts the PV down if the network fails.  Some may require an export limiter to prevent the PV exporting to the grid. Some will not give permission if the local network is not capable of dealing with the fault level represented by all the connected generating loads (e.g. PV's, Wind Farms, CHP and battery systems) on the local network.