Photovoltaics

What are they?

Photovoltaic (PV) panels generate electricity from sunlight and are typically referred to as ‘solar panels’. PV panels are different to solar thermal panels which utilise sunlight to heat water. PV panels need direct line of sight to the sun, so are usually mounted on a north facing pitched  roof or on a flat roof using an A-frame (facing north) to support them.  Electricity generated can be consumed by the building to which they are attached or exported and sold to the electricity grid.

Advantages / Disadvantages

Provide a strong and visible environmental /  sustainability message.

Low maintenance as panels need periodic cleaning only.

Limited capacity relative to building demand for many building types.

High installation costs, although these have reduced remarkably over the past 5 years to the point where they are competitive with some efficiency measures,

The technology is only appropriate to use on buildings with good solar access for much of the day

Energy efficiency

A PV panel uses sunlight to generate DC electricity that can be converted into AC electricity and used in the building. This reduces the energy required from the national grid. Excess electricity produced by the PV panels can be exported back to the electricity grid.

Running costs

The electricity generated will reduce the amount of energy purchased from the grid, thereby reducing running costs.

Formerly generous feed-in tariffs have been abolished, but exported electricity is generally being bought back at wholesale prices (around 7.5c/kWh).  Optimum return on investment is achieved where  the amount of export is minimised.

Retrofit / improvement opportunities

PV panels should work effectively for at least 25 years after installation before needing replacement. The DC / AC invertors will typically need replacing once over  this period.

PV panels can be easily retrofitted to a roof with adequate accessible space and where an unshaded north facing orientation can be  achieved.

Consideration also needs to be given to roof loadings, electrical safety requirements, the safety of roof access and the avoidance of any compromise of the watertightness of the roof.

Applicable buildings

All buildings with available roof space and where an unshaded north facing orientation can be achieved will benefit from the application of PV  panels.

Floor plate implications

None.

Occupant comfort

No issues.

Maintenance implications

PV panels are very low maintenance as only periodic cleaning is required.  The DC / AC invertors located inside the building typically require replacing  every 15 years.

Identification

PV panels will normally be on the roof and orientated to receive maximum  sunlight. The panels have a shiny / reflective appearance and there will  be electrical connections to them. There will not be any insulated water  pipework connected to the panels.

Questions to ask

• Who owns the PV panels?
• Who in the building receives the power that the PV panels generate?
• What costs / savings do the panels create for the tenant?
• Was the system registered for the Feed-in Tariff and if so, who gets    the income generated?

More information

References required