Solar Jargon

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A type of PV solar cell. Unlike multicrystalline and monocrystalline cells (see below), amorphous panels are not made from interconnected solar cells made from expensive crystalline silicon.

Instead, a very thin layer of silicon is sprayed on to a backing material to make solar roof tiles. As the silicon is much thinner than the silicon wafers in a typical crystalline solar cell, material costs are greatly reduced.

Active solar
Using a collector, e.g. a solar panel, to capture the sun’s energy and use it to heat water or convert it to electricity.

Drain-back system
A solar water heating system where the water inside the solar panel drains into a small back bottle when the pump switches off. This protects the system against damage due to boiling and freezing, without the use of antifreeze.

Evacuated tubes
A type of solar water-heating panel. Evacuated glass tubes collect the sun’s energy and heat water running through a container at the top of the tubes.

Feed-in Tariff
The Feed-in Tariff scheme allows you to sell any unused or excess electricity to the national grid. For a detailed guide to the FIT and a useful cashback calculator to see how much income you could receive, check the Energy Saving Trust’s guide to the FIT scheme.

‘Free solar’ or ‘Rent a roof’ schemes
Schemes where companies pay for the cost of installing solar panels on your roof, and then generally take all of your Feed-in Tariff income.

Passive solar
Capturing the sun’s energy without a panel or collector, e.g. through large south-facing windows, and minimising heat loss through insulation.

Photovoltaics, PV
PV cells are thin layers of semi-conducting material (usually silicon). Electrical charges are generated when the silicon is exposed to light, which can be conducted away as direct current. Multiple cells are connected together (usually behind glass) to form a panel.

Pressurised system
Water is pumped through the solar panel and heated. This heated water flows through a heat exchanger, warming the water stored in your hot water cylinder. These systems typically use antifreeze.

Renewable Heat Incentive
A financial support scheme for generating heat, similar to the Feed-in Tariff for generating electricity.

Solar tiles
Solar tiles use the same technology as photovoltaic cells, but are smaller and narrower than large PV panels and look like roof tiles.

Solar water heating
Water is pumped through a solar panel and heated by solar energy. The heated water then flows through a heat exchanger, warming the water in your hot water cylinder.

Monocrystalline silicon cells
The most efficient and expensive PV cell. Cut from single crystals of silicon, this system can harness around 15% of the sun’s energy that falls on it.

Multicrystalline silicon cells
PV system made from silicon cut into wafers. It’s slightly less efficient than monocrystalline cells, but also slightly cheaper.