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Siward House - Sheltered housing scheme
Siward House is a sheltered housing scheme in Petersfield, close to the town centre. It holds 34 apartments, providing accommodation for the over 55s. In February 2007, a solar photovoltaic (PV) panel was installed, in order to supply free electricity to all the communal areas of the scheme.
Siward House photovoltaic (PV) energy
Siward House now has 33 PV panels installed 31 m2 on the roof. These panels are collecting energy from the sun and producing electricity to run lighting and communal appliances. The panels started operating on 14 February 2007.
What are photovoltaics?
Solar photovoltaics (PV) is a 'green' renewable energy system that uses energy from the sun to create electricity. PV requires only daylight, not direct sunlight to generate electricity and so will still generate power on a cloudy day.Siward House display panel
There is a display panel by the main door at Siward House. The panel shows three different types of data. The top figure shows how much energy is currently being produced in KW (kilo watts). The second figure shows how much carbon dioxide has been saved since the system was commissioned. The bottom figure shows the total units of electricity generated by the system since installation.How does it work?
1. Photovoltaic systems are made up of cells that convert sunlight into electricity. The PV cell consists of one or two layers of material, usually silicon, which absorb sunlight to generate electricity. When light shines on the cell it creates an electric field across the layers causing electricity to flow. The greater the intensity of the light, the greater the flow of electricity.
2. The electricity generated by the PV panels is fed into a box called an 'inverter'. The inverter converts electrical power from Direct Current (DC) to Alternating Current (AC), which is used in homes. The inverter also regulates the amount of electricity needed from the national grid to top up the electricity supplied from the panels.
The inverter can also export excess electricity produced by the panels, effectively selling it back to the electricity supplier. However, this only happens if the panels are producing more power than the communal areas of Siward is consuming, which will be infrequent.
3. A two-way meter records power used and power sold back to the National grid.
4. The consumer unit measures consumption.
The costs
- The PV system cost
24,000 (11,000 contributed by the Government) to install. - The panels are guaranteed for 25 years but are expected to have a minimum life of 40 years.
It is estimated that the pay back period will be somewhere between 3050 years, so it is clearly a long-term solution.
The electricity produced from the system is free. We conservatively estimate that we will save at least 320 per year. In addition to this we will also receive further money back from our supplier in the form of ROC֒s (Renewable Obligation Certificates) which will potentially double the income.
The benefits to the planet
The Siward House PV system is expected to generate at least 3220 units of electricity each year, enough to run the average house. Using this technology Siward House will reduce its emissions of carbon dioxide by a minimum of 1.5 tonnes each year!
