On-site renewable energy

The planners are asking for on-site renewable energy for new buildings. Many are following the 'Merton Rule' which requires new developments to generate at least 10% of their energy needs from on-site renewable energy.

Consider your options:

	Generates electricity	Captures solar heat	Stores heat between seasons	Delivers space heating	Energy losses on Conversion	Note
Photovoltaic		X	X	X	high
Wind turbines		X	X	X	high	Needs planning permission
Combined Heat and Power		X	X		low	Releases CO2
Biomass	X	X	X		low	Releases CO2
Solar water heating	X		X	X	minimal	Works better with IHT™
Ground Source Heat Pumps	X	slowly	partly		minimal	Works better with IHT™
IHT™	X				minimal	Invisible, no noise.

Photovoltaics

Photovoltaics convert sunlight into electricity with an efficiency which has been as low as 15% but new technology is improving this: this option can be considered where the use of electricity matches periods of sunshine or where electricity is required some distance from a publicly available supply.

Wind Turbines

Wind turbines can convert wind into electricity – when a constant wind is blowing at near to the optimum speed. The electricity provided depends on the strength of the wind which may not match the electricity demand profile of your building. Electricity is difficult to store, although you may be able to sell a surplus to the Grid (at a low price) and can buy electricity (at a higher price) when the wind is not blowing. You will need to allow for planning permission on large installations. Generally the electricity generated by a wind turbine increases with the wind speed, the size of the blades, the height above the ground, the distance from other buildings and the distance (in the UK) from London.

Combined Heat and Power

Combined Heat and Power systems generate electricity from burning fossil fuels and capture the heat generated in the process for heating purposes. Although CHP burns fuel and releases CO2 it can work with high efficiency and therefore releases fewer greenhouse gases than remote fossil-fuel-powered electricity generation which usually wastes the heat produced as a by-product of generation (and also wastes some electricity in transmission to your site). CHP can be used where there is a significant year-round need for heating, in addition to the electricity generated.

Biomass heating

Burning biomass does not consume fossil fuels, but it does release CO2 into the environment. These mechanisms require management, but can work well if there is a ready supply of cheap local biofuel.

Solar water heating

Solar water heating can provide pre-heating of water prior to raising temperatures to the required level: these mechanisms can capture heat efficiently and can be effective where a high volume of hot water is needed at the same time as the sun is shining. Retrofitting is often an option. Problems arise when hot water is needed at a different time from when it is collected, as it is difficult to store heat over a period. Heat can be stored overnight in hot water tanks, but if heat is not required when it is collected it will probably be wasted. The best time for heat collection (in the long hot days of summer) may not match the time of greatest need (in the long cold nights of winter). Overheating can also arise when there is no hot water demand in the peak collection period – summer holidays – as it is not possible to switch off a solar collector.

Ground Source Heat Pumps

A Heat Pump can separate warm temperatures into hot and cold: the heat obtained may be 3 or 4 times the amount of electrical energy needed to run it. A Ground Source Heat Pump draws heat out of the ground by means of water circulating in pipes beneath the ground: as the ground gets colder the Heat Pump must work harder to obtain the heat required. If there is no active mechanism to replace heat taken from the ground it will take time for heat to migrate toward the “heat overdraft” created.

This is a key problem for Ground Source Heat Pump systems: heat only moves very slowly in the ground. The solution is below.

Interseasonal Heat Transfer™

ICAX adds a solar collector and a Thermal Bank™ to a heat pump interfaced with a sophisticated electronic control unit. Surplus solar heat collected in summer is deposited in the patented Thermal Bank™ in the ground. This raises the temperature of the Thermal Bank from the natural temperature of the ground, 10°C, to over 25°C over the summer months. In winter the heat pump draws warmth from this Thermal Bank in place of starting with a cold temperature from the ground. This allows the heat pump to generate more heat from less electricity. This improves the Coefficient of Performance and transforms the economics of the heat pump. In comparison to a standard GSHP installation ICAX provides a short cut to the primary power source – the sun.

ICAX uses the same equipment and mechanisms in reverse to provide cooling to buildings – at a much lower cost in electricity and CO2 than traditional air conditioning equipment.

IHT™ is powerful, invisible, efficient and in tune with the natural environment.

See Report on IHT by Transport Research Laboratory.

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