Solar Photovoltaic

PV installation on school roof(Source: Belfast Education & Library Board)
PV installation on school roof(Source: Belfast Education & Library Board)

Solar energy can be directly used for electricity generation through photovoltaic panels. Design of the building and PV system should take place together to enable solar orientation for optimal PV energy generation.

Photovoltaic (PV) systems convert energy from the sun into electricity through semi-conductor cells, most commonly made of silicon. When sunlight falls on a cell it creates an electric field across the layers, causing electricity to flow. The efficiency of PV panels varies according to type of material used. Lower cost amorphous cells are less efficient compared to silicon cells up to at converting solar energy into electricity.

Some materials are less sensitive to directional solar radiation than other. PV panels are usually connected to an inverter to turn direct current (DC) produced into alternating current (AC). AC is used in buildings or can be exported to the electricity grid. The inverter may need to be replaced every 5-10 years, the PV itself has a lifetime of over 25 years.

There are a number of types of PV cell which vary in efficiency and cost. A range of formats can  be obtained including roof tiles, shingles (look like asphalt shingle), bolt-on modules, cladding, integrated into standing seam roofs and integrated into glass laminate for facades, walkway canopies or atrium roofs. These can be used to either blend into the existing setting or as a design statement. The suitability of the different type depends on the building type and whether the project is retrofit or new-build.

Panels need to be installed within 30˚ of a south facing orientation or be mounted horizontally for good performance and they should not be shaded.

Optimal orientation of building to maximise PV output

There is a high capital cost to purchase the panels but maintenance costs are minimal. The ‘feed-in-tariff’ means that running costs can be significantly offset. Commissioning of the system, grid connection and metering issues need to be agreed with the local Distribution Network Operator.

Link to short examples

What should I do?

Ensure that orientation and overshadowing issues are considered to maximise performance.

WLGA - CLILC Llywodraeth Cynulliad Cymru / Welsh Assembly Government