Earth Notes: Glossary of Technical and Green Terms

Locally-generated (distributed) energy generation, eg from renewables such as solar, often owned and run by a non-profit group. See What is community energy?

Also known as:

• Distributed generation

Warms or cools a building by transferring heat from a relatively low-temperature place to a hotter one. Domestic heat pumps can be ground-source or air source (where they move heat from when heating) and can heat via a wet heating system (radiators, underfloor, GSHP, ASHP) or to air (eg air-to-air mini splits).

Also known as:

• ASHP
• GSHP
• air-to-air

A common type of battery with lead plates and a sulphuric acid electrolyte. Initially invented in the late 1800s. Used in many applications from cars and other motor vehicles through to electric vehicles, and storage for on-grid and off-grid renewable energy. Comes in common variants such as flooded, AGM and gel, and often in multiples of 12V. Very good support for chargers, solar controllers, etc. Lead-acid batteries generally do not take well to being discharged such that the SoC (State of Charge) is under 50% of full charge any significant amount.

Also known as:

• lead-acid
• Flooded Lead-Acid (FLA)
• Advanced Glass Mat (AGM)
• Sealed Lead-Acid (SLA, including gel and AGM)
• gel
• PbSO4

A Lithium-chemistry battery known for resistance to overheating and fires compared to Li-ion, at the cost of a slight reduction in energy density. All Lithium batteries need relatively careful management, eg with a BMS (Battery Management System), but are notably able to be discharged to a much lower SoC (State of Charge) than lead-acid batteries typically.

Also known as:

• Lithium Iron Phosphate
• LiFePO4

A method to improve ventilation while retaining heat (or cool) in a building. In other words, achieve fresher air and lower energy bills. This is accomplished with a heat exchanger between in-flowing and out-flowing air, often a counter-current heat-exchanger. Sometimes the flows enter and exit the building via a central unit. With Single Room MHRV (SRMHRV or SRHRV) the mechanism exchanges air directly through an exterior wall in each equipped room.

Also known as:

• MVRH (Mechanical Ventilation with Heat Recovery)
• SRMHRV (Single Room Mechanical Heat-Recovery Ventilation)
• SRHRV (Single Room Heat-Recovery Ventilation)
• HRV (Heat Recovery Ventilation)
• ERV (Energy Recovery Ventilation)

Device or system to generate electricity from light, often sunlight, for example using solar panels on the roof of a building. Electricity produced by a solar PV system can be used locally, stored locally, or exported to an existing local grid, as determined by cost and technical factors. Solar PV comes in a number of forms, but common types are silicon monocrystalline, polycrystalline and amorphous.

Also known as:

• solar power
• solar panel
• solar cell
• monocrystalline PV
• polycrystalline PV
• amorphous PV

A TRV (Thermostatic Radiator Valve) automatically regulates the temperature in a space by controlling the amount of hot water entering the radiator of a "wet" or "hydronic" (often central) heating system. Once some but not all rooms come up to ther desired temperature, a TRV saves energy and improves comfort by avoiding rooms overheating, which static balancing alone of a system may not achieve. OpenTRV/Radbot is a smart TRV.

Thermal imaging can be used (amongst many other things) to detect heat loss from homes to work out where to fix insulation and ventilation and other building fabric issues to save energy. Thermal imaging works by using heat given off by surfaces as infrared (IR) light. Special IR cameras are needed to capture this since IR is blocked by typical glass camera lenses.

Also known as:

• thermographic imaging
• thermographic photography
• thermographic camera
• infrared imaging
• IR imaging
• thermography

A wind turbine, often for generating electricity, that spins around a vertical axis. Common designs of VAWT include Darrieus and Savonius. Compare with the more common HAWT (Horizontal-Axis Wind Turbine.

Also known as:

• wind turbine
• windmill
• transverse axis wind turbine
• cross-flow wind turbine

Wet or hydronic central heating circulates hot water from a boiler or furnace or heat pump through radiators, underfloor pipes, towel rails, etc, to heat a building. As of 2022 it is by far the most common form of domestic heating in the UK, with the boilers being powered by combustion of natural gas. These gas boilers in 20+ million homes will be replaced for the most part with heat pumps over the next few decades to help eliminate carbon emissions and tackle climate change. Wet heating is generally quiet and safe and efficient compared to fireplaces or electric heaters or portable heating appliances.

Also known as:

• radiator central heating
• hydronic central heating
• wet space heating