Photo = light & voltaic = electricity

Photovoltaics is a technology that utilises light to generate electricity. As such it is an essential tool in the development of more sustainable methods of electricity generation. Simplistically, electricity is generated by the photons from sunlight colliding with electrons within the solar cell.

Solar cells are solid state devices that produce direct current electricity from light. They are arranged into interconnected groups to form a module. In turn photovoltaic (PV) modules are connected together into photovoltaic arrays. A module is big enough to power a single device with larger applications such as a family home requiring an array. PV arrays can be built into the fabric of a building, in its roof or walls, or developed as a stand-alone system as we see connected to street lights or on caravans.

PV cells use both direct light and indirect or diffuse light and so are effective even in temperate climates and operate under grey overcast skies, not just on bright sunny days.

As in most cases they constructed largely from silicon, the manufacture of PV modules has relatively green credentials, although the need for batteries for storage in off grid situations can somewhat sour this.

Most UK implementations of PV will be grid connected PV systems. In these systems there is no need for battery storage. The PV system is connected to the local electricity network (grid) and any electricity not consumed locally can be sold to the electricity supply company. Where the local PV system is unable to provide all electricity demanded, for example at night, then electricity is bought from the grid. The ‘grid’ acts as the storage system.

An inverter will be required to convert the low voltage (12 volt) DC electricity generated by PV to high voltage (230 volt) alternating current (AC) consumed by most UK appliances.

How much?
A typical domestic system will need between 1500 and 2000 Watts peak (Wp)
Typical modules have power output of 75 to 120 Wp.
Therefore, 10 to 20+ modules will be required.

I have ‘tirelessly’ searched the internet for illustrative costs from various sites and articles of various ages I’ve come up with the following:

£4,000 to £9,000 per kWp installed.

£8,000 and £15,000 on a typical domestic installation of 1.5 kW.

…this works out at £12 000 - £14 000 for a 2 kWp system for a house.

To provide a PV power supply capable of meeting the demand from a typical domestic energy efficient house costs in the region of £20,000.

…costs can be around £5,000- £8,000 per kWp installed with most domestic systems usually between 1.5 and 3 kWp.

Which gives an average of somewhere around £6,000 per kW so £10,000 for a typical domestic installation of 1.5 kW. As this will save you several hundred pounds a year on electricity costs the financial payback is long. The overall cost-benefit will only tip into the positive if you personally value the ecological benefits highly.

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Solar water heating systems use energy from the sun to heat water for use in the home. This water can be utilised for washing and general domestic uses as well as for heating purposes.

There are three main components:

1. Heat Collectors or Panels. The two main types are flat plate and evacuated tube both are normally fitted onto roofs but can be ground mounted. Evacuated tube systems use metal strip collectors in vacuum tubes and are the smaller but more expensive option. Flat plate systems use a dark coloured plate in an insulated container collect heat.
2. Heat transfer system. Transfers the collected heat to the water.
3. Hot water cylinder. This stores the heated water and supplies it onward to those systems that consume it.

In the UK, appropriately sized systems can provide up to 90 per cent of the hot water needs of a typical home.

Depending on specifics such systems should cost upwards of £1,000 in a new build domestic property with higher initial costs for a retro-fit. From recent research it should be possible to install system for £4,000-£5000 into the average home. Payback may be up to twenty years, but with current fuel price escalation this is likely to drop rapidly.

Designing a system to meet your needs will require consideration of supplementary heating systems, the site and its orientation to the sun (you will need some south-facing aspect), the heating & hot-water requirements of the buildings inhabitants and budget. As we in the UK are not overly endowed with sun during the winter months you will also need a supplementary heating system to provide hot water when the sun can’t - log, pellet, gas and multi-fuel burners and boilers can fulfil this role if configured correctly within the overall system.

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I feel like I’ve somewhat misrepresented pellet stoves in the past.

To recap, pellet stoves are wood burners with a difference, they burn pellets made from pressed waste wood, that are feed from a hopper into a combustion chamber all of which is often controlled electronically.

I’m sure no-one has really been reading who’ll take offence, but I feel that I should redress the balance. When writing about biomass heating, I stated that:

biomass systems are often bulky and so can require extensive storage space for both fuel and machinery

…with no statement of assumptions and seemingly no exceptions.

After further research, I’ve found some nifty looking pellet stoves such a those from Rika, that offer full biomass credentials whilst remaining compact in size and offering levels of control not available with more crudely fuelled wood or multi-fuel burners. I especially like the Rika option that allows remote control of the system by mobile telephone. Read More

So, to redress the balance: Biomass can be compact as well as clean and green!

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The term biomass heating refers to the combustion of plant based organic materials for the purpose of heating a volume of air. Biomass fuels fall into two main categories:

Woody resources from sustainable sources such as fast growing trees or subsiduary waste products such as sawdust or recycled untreated pallets.
Non-woody resources such as animal waste […]

The younger sibling of the ground source heat pump (GSHP), the air source heat pump (ASHP) is an exciting development in heating technology. They operate on the same principles as the under-ground alternative, but draw thermal energy from the air rather than underground - air at ambient temperatures is passed over a finned heat exchanger […]

The basis of heat pump technology is something that we are all familiar with as it is the same as that used in refrigerators or air conditioning units. The core function of these units is to take heat from the ground and transfer it to a building for the purpose of heating water. This heated […]

From the Romans to present day, underfloor heating has been a good idea. Underfloor heating provides gently radiating heat from the whole of the floor surface. This radiant heat is similar to the heat from the sun, heating the occupants of the room directly rather than the air around them (must admit I’ve never fully […]

Through recent technological innovations it is now possible to insulate buildings to such an extent that no heating system is required to maintain comfortable temperatures.
There are varying categories of super insulated buildings.
Zero Heat Building
This category of building, through insulation and draft proofing, requires no additional heat source, except for in extreme conditions. The heat provided […]

Rainwater harvesting is one of those simple concepts that reminds us of old-fashioned sensibilities. Basically, it entails the collection of the rainwater that falls onto a roof, the storage of that water and its utilisation for domestic purposes.
The water is collected by normal roof gutters then passed through a filter to remove dirt, leaves […]