Edinburgh World Heritage - Microgeneration

 

Microgeneration

Renewable Energy’ is energy that comes from a constant and sustainable source, which does not harm the environment.

  • Heating: Solar hot water, Biomass Heating, Ground Source Heat Pump, Air Source Heat Pump
  • Electricity: Photo-voltaic, Micro-Hydro, Wind
  • Heating and Electricity: Biomass CHP (combined heat and power)

Generating Your Own Energy

Save money by generating your own energy. Feed-in tariffs enable households to install renewable energy technologies to claim payments for low carbon electricity they produce.

As an example, a typical domestic solar electricity system with an installation size of 2.7 kWp could earn around:

  • £530 per year from the Generation Tariff
  • £40 per year from the Export Tariff
  • £100 per year reduction in current electricity bills.

This gives a total saving of around £670 per year.

This assumes a well oriented, un-shaded system, and 75% of the electricity generated exported. This figure will be lower for less ideal installations, and slightly higher if more of the electricity is used directly in the home.

Traditional ‘fossil fuel’– oil, gas and coal

Fossil oil took 500 million years to be created from plant substances, hermetically sealed and under high pressure. Fossil energy has a high energy content compared to what is gained with renewable energy. In the last 100 years more than half of the known resources have been used. Recoverable resources are expected to last around 40 years for oil, 60 years for gas and 130 years for coal.

Solar Water Heating

Visible installations will probably not be allowed on listed buildings or in a conservation area however panels may be able to be hidden in valley of ‘M’ shaped Georgian roofs.

Solar eating provides hot water at 55-65ºC and can provide all hot water needs in summer. It can be mounted on the roof or integrated into the roof covering (this is especially viable when roof cover needs replacing). A system comprises solar panel or tubes, a heat transfer system and a hot water storage cylinder.

  • It should be south-facing; too much shading can reduce energy performance.
There are two types of solar heating: a flat plate (most common, slightly less efficient, bigger and cheaper), which turns 65-70% of the solar energy into usable heat or evacuated tubes (slightly more efficient and slightly smaller but more expensive), which have an efficiency of 80-85%.
  • In Scotland, a standard 1m2 panel can generate around 450 kWh of energy per year. A typical system of 3-4 m2 should provide all hot water needs in summer, around 50% of the annual demand, and will cost around £4,000
  • You will need to consider the roof area available, the type of boiler/fuel you use for hot water and space for a storage tank.

Solar Photovoltaic (PV)

PV cells convert sunlight into electricity. Nowadays an array of different PV cells exist with different efficiencies and costs and those harvesting diffuse light (not subjected to direct sunlight) have become more effective over the years. Photovoltaic can be incorporated as panels, PV tiles replacing roof tiles or PV cells in or on glazing.

  • Theoretical maximum efficiency of around 30%
  • Roof-mounted cells are most efficient in bright sunlight, so south orientation is preferable, ideally at a 20-50 degree angle.
  • An average system of 10-15 m2 (107-160 sq ft) should provide about half of the average family’s electricity needs
  • A typical solar photovoltaic system will costs around £10,000, but you can generate around £670 per year income through the feed-in tariff.

There are virtually no running costs if connected to the grid; however, the payback period on PV panels is very long.

Biomass

Biomass stoves and boilers supply heat or hot water to buildings. The term biomass includes a variety of organic material, such as trees and organic waste. Biomass creates CO2 emissions. However, burning wood only emits as much CO2 as the tree absorbed while growing, making it ‘carbon neutral’. A biomass stove may be located in a living room, whereas a biomass boiler is larger and may be located in a separate utility room.

Consider in advance the location and the size of the boiler including the flue and the feeder, and the space for storage requirement of fuel, such as logs, pellets and woodchips.

  • Biomass is especially sustainable when locally sourced.
  • The best biomass systems can be over 90% efficient, their cost effectiveness depends on the type of fossil fuel displaced and the type of wood used.
  • A wood-burning stove can cost anywhere from £500 to £3,000 to install. A biomass stove (6-12 kW) costs around £3,000. A 20kW biomass boiler costs between £10,000 and £15,000.

You can retrofit your wood burning stove in your unused fireplace; vents can be installed in the ceiling to provide heat also to the rooms upstairs.

Heat Pumps

Heat pumps use the warmth from the air or ground to create heat for heating and/or hot water. A heat pump uses electricity but uses only 1 unit of electricity compared to the 3-4 units of heat it provides (a conventional boiler will only produce about 0.8-0.9 units of heat from a unit of electricity). The reverse process can be used for cooling.

  • A heat pump has an efficiency of about 300%.
  • A ground source heat pump (GSHP) used for heating is often cheaper than using oil, LPG or electric storage heaters, based on current fuel prices. Cost effectiveness usually depends on the type of heat distribution system (e.g. radiators, under-floor heating, etc.) you have.
  • The efficiency of an air heat pump, which uses external air, is unreliable due to temperature fluctuations. The temperature in the ground is constant at around 10 degrees Celsius.
  • GSHP using deep boreholes is most common and may cost around £10,000.

A heat pump runs constantly and uses constantly electricity. For a GSHP you will need access and space to drill a borehole or dig a trench.

Micro-Combined Heat and Power (CHP)

The heat from the generation of electricity is used for space heating, which is otherwise lost at large power plants. Domestic CHP units vary in size and output. It is a renewable system when running by biomass; gas or oil can also be used and there will be a higher gain from the fuels.

  • They can be linked to batteries or fuel cells to store electricity.
  • 35% of primary energy can be reduced comparing a CHP with a power station and heat-only solution.
  • Most efficient and cost-effective when operated on a district-wide scale where it can run continuously. To be effective, it needs to be located near the end-user to prevent long connection losses.

Micro-Wind Turbines

These generate electricity from wind and they can be roof-mounted or stand alone. Their potential output depends on the location, the surrounding environment and its average wind speed, which needs to be at least 4m/s to be economically attractive.

  • Not usually recommended for city locations as it is visually intrusive and noisy, and unlikely to get LBC.
  • A wind turbine has a theoretical maximum efficiency of 59%, running at full power generally for less than 10-15% of the year.
  • A mid-range domestic turbine of 2.5kW may cost around £11,000 – £13,000

A wind turbine was installed on the roof of the John Hope Gateway building at the Royal Botanic Garden in Edinburgh.

Micro-Hydro

Micro-hydro systems use the natural water courses and are capable of continuous generation (unlike wind generators for example). Although water flow is likely to be low in summer, hydro systems are very energy efficient.

  • Not recommended for city locations.

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