What are the popular renewable energy options?

Do you know your PVs from your CHPs? Well don’t worry neither did Adam's mum until he sat down and explained it to her. We don’t like the clever-clogs approach to advising on energy efficiency and renewables. ‘Keep it simple’ is our mantra.

In this section we’ve listed a few details on the most popular options you might consider when integrating energy efficiency or renewable technology into your home or business.

We’ve rated each on a scale of one to five in terms of:

Energy efficiency – How we rate a technology’s ability to generate or save energy and the usefulness of that energy to you
Installation practicality – How easy is it to get approval for and install this technology
Financial costs and benefits – a rating based on the initial and on-going cost, the potential income (from Government-backed renewable energy grant schemes) and savings of the system

We believe the key to a decision to invest in any form of improved energy efficiency has to be pay-back. In other words, how long will it take you to get your money back?

If there are Government subsidies involved, you also need to calculate what return on investment you are going to make over say a 10 year period. This can make the case for seemingly expensive systems far more compelling.

Also you need to think carefully about what single or combination of systems is going to work best for you. It is never a case of one size will fit all.

Solar Electricity (Photovoltaic or PV)

Creating solar electricity from the energy of the sun is done by sunlight touching a photovoltaic cell (lots of photovoltaic cells make up a photovoltaic panel and a number of panels are needed to generate sufficient power for a house).

The sunlight triggers an electronic reaction in the cell, which creates an electrical charge. The combination of the charges from these cells, and then the combination of charges from a number of panels, becomes usable electrical power. The electrical power is then converted from DC (Direct Current) into AC (Alternating Current), the form we use electrical power in our houses, by passing it through something called an Inverter. The current then passes through a generation meter, to record the electrical power produced and then directly into the main fuse board of the house, from which all electrical sockets and lights get their power.

Solar generated electrical power that is not used in the house is fed out into the local power network (the Grid) through an Import/Export meter, which records how many units of power are being exported.

Photovoltaic, or PV cells don’t need a clear sky to operate and will still work on cloudy days – although generally speaking, the brighter the day the better the performance of the solar panels. The solar panels are best sited in south facing areas (roofs or open land) and away from shade cast by other buildings or trees.

Government grant available

Finance packages available

Energy efficiency

Installation practicality

Financial cost benefit

Solar for Hot Water

Creating hot water from solar energy is done by using the heat of the sun to directly warm a liquid contained within a sealed panel.

“Wet” solar panels are made up of either a row of glass tubes or a flat panel, each with the air removed from inside to make the passage of heat between glass and liquid more efficient. The solar panels are best sited in south facing areas and away from shade cast by other buildings or trees. The heat of the sun warms the liquid in the solar panels, which is then pumped through a hot water cylinder to warm the water inside the cylinder.

Very high temperatures can be reached with these solar based systems (sometimes over 200C on the exposed panels themselves). Therefore, the flow of liquid around the system and the use of the hot water it creates, is as important for cooling the system as heating the water, so sizing is critical. Hot water temperatures in summer can easily exceed 90C and could contribute up to 50% of a building’s hot water needs.

Government grant available

Finance packages available

Energy efficiency

Installation practicality

Financial cost benefit

Air Source Heat Pumps

An air source heating system takes heat from the sun, stored in the air around a building, and transfers it to the water that circulates around the heating system in the building.

A fan (outside) pushes air over a heat exchanger, which transfers the heat to a special liquid (a refrigerant liquid). The heat from the air turns this refrigerant liquid into a gas which, when put under pressure by a compressor, becomes much hotter. This hot refrigerant gas is then pumped into the building and into another heat exchanger; the new heat from this hot refrigerant gas is then transferred to the water of the building central heating system (at up to 75C). This heated water is then pumped around the building via under-floor heating systems, radiators, and with some systems, also into the hot water tank.

Because of something called the “coefficient of performance”, an air source heat pump can take 1 unit of energy (electricity to run pumps and compressors) and turn it into 3 to 4 units of heat. Like ground source heat pumps this clever bit of physics is the basis for their existence.

Government grant available

Finance packages available

Energy efficiency

Installation practicality

Financial cost benefit

Ground Source Heat Pumps

A ground source heating system takes heat stored in the ground around a building and then transfers it to the water that circulates through an existing heating system.

A liquid is pumped through a long length of pipe either buried under the ground over a large area or drilled straight down in the form of a borehole. The liquid absorbs heat from the ground (at about 10C-15C) as it moves along the piping and then returns to the building and flows through a heat exchanger, which transfers the heat to a different special liquid (a refrigerant liquid). The heat from the ground turns this refrigerant liquid into a gas which, when put under pressure by a compressor, becomes much hotter. Whilst still in the heat exchanger, the new heat from this hot refrigerant gas is then transferred to the water of the building central heating system (at 45C-55C). This heated water is then pumped around the building via under-floor heating systems or radiators. Due to the lower operating temperature of the heated water, this system is not suited for ‘hot’ water supply and cannot always be fitted to existing radiator systems.

Because of something called the ‘coefficient of performance’, a ground source heat pump can take 1 unit of energy (the electricity used to run pumps and compressors within the unit) and turn it into 3 to 4 units of heat. As in air source systems, this clever bit of physics is the basis for their existence.

Government grant available

Finance packages available

Energy efficiency

Installation practicality

Financial cost benefit

Biomass Boilers

A biomass boiler provides hot water and heating for a building in the same way as a boiler fuelled by gas or oil.

The fuel source (what it burns to generate heat) used by a Biomass Boiler is wood or another form of naturally grown product (such as grass, agricultural products or fast growing woods like Poplar or Willow). Wood can come in many forms such as logs, chips or pellets, with pellets being the most common and easy to use. Pellets are small (5-10mm) cylinders of sawdust, generally dried to a very low level of moisture.

The fuel for a Biomass Boiler will need to be provided on a regular basis by a local supplier, either in bags or by being “blown” from a truck into a hopper or storage tank. Biomass boilers are generally best seen as a renewable energy solution for those with plenty of storage space and easy access for Biomass fuel supplies.

Government grant available

Finance packages available

Energy efficiency

Installation practicality

Financial cost benefit

Rainwater Harvesting

Rainwater harvesting systems collect rainwater from your roof or other surfaces, and store it for use in non-potable situations (situations where the water is not going to touch your lips), such as washing machines, toilets, garden watering and car washing.

These rainwater harvesting systems store the rainwater in underground tanks (to save space) and use filters and pumps to provide clean, cold water into a building. The water is also provided at typical mains pressure so it looks like it is just coming from your normal water system. However, whilst additional filters and cleaners can be installed to turn the rainwater into drinking water (an expensive add-on), it is important that the rainwater harvesting system has its own pipes inside the building to avoid mistaken use of rainwater for a purpose for which it is not meant.

Government grant available

Finance packages available

Energy efficiency

Installation practicality

Financial cost benefit

CHP (Combined Heat and Power)

Combined Heat and Power systems use one source of fuel to generate both heat and electricity.

These CHP systems can therefore be efficient methods of satisfying one energy requirement (heating and hot water) but satisfying another (electricity) as a by-product. A typical gas boiler system might use excess heat to drive a Sterling engine (don’t ask!) to create electricity, or an electricity generator might use excess heat to warm a building or a water supply.

Combined Heat and Power systems have typically been more relevant in larger scale commercial situations but increasingly domestic size CHP systems are becoming available although they are still fairly rare things to find in someone’s house.

Government grant available

Finance packages available

Energy efficiency

Installation practicality

Financial cost benefit

Wind Turbines

Wind turbines take the energy in the wind and turn it into electricity.

Wind turbines are best sited in open, elevated areas, as far away as possible from obstructions, such as houses, buildings or large trees. The blades on the turbine (the windmill bit) are turned by the wind, which in turn drives an electrical generator. This electrical generator converts the turning motion of the blades into electrical power (the reverse of an electrical motor, which converts electrical power into a turning motion). The electrical power is then converted from DC (Direct Current) into AC (Alternating Current), the form we use electrical power in our houses, by passing it through something called an Inverter. The AC Current then passes through a generation meter, to record the electrical power produced and is then fed directly into the main fuse board of the house, from which all electrical sockets and lights get their power.

Electrical power that is not used is fed out of the house into the local power network (the Grid) through an Import/Export meter, to record what power is exported.

Government grant available

Finance packages available

Energy efficiency

Installation practicality

Financial cost benefit

Heat Recovery and Ventilation

Heat Recovery and Ventilation (sometimes known as Mechanical Heat Recovery MHRV or HRV) systems collect, ‘clean’ and then re-circulate air within a house or office building.

By ‘re-using’ existing warm air, your central heating doesn’t have to work so hard to heat your house.

As we all remember from our school science lessons, hot air rises, so these Heat Recovery and Ventilation systems work by capturing warm but stale air that has already been heated through central heating - usually on the upper floor of a house, bathroom and kitchen. This air is then channelled through ducts (flexible tubing) into a Heat Recovery Unit normally situated in a loft. This part of the HRV unit collects the heat from the waste air, filters out dust, pollutants and pollen and then mixes it into fresh air collected from a vent in the roof or wall. This air is then sent back into the house through vents located in ceilings.

Finance packages available