Generate Renewable Energy
Westmill is home to two different renewable energy sources: wind and solar. This is a unique feature of the site and means that we can show how both technologies work.
Each year, our technology produces a combined total of over 10 GWh of clean, renewable energy. That is enough energy to boil 3,300,000+ kettles, watch 14,300,000 hours of television or power over 4,000 homes for a whole year.
Our stats...
What happens at Westmill?
Community-owned renewable energy co-operatives are an integral and innovative solution to the climate crisis and diminishing fossil fuel reserves. As renewable energy sources, both wind and solar energy production rely on naturally occurring sources of energy which will not run out. Although they work in different ways, both wind turbines and solar panels take these renewable energy sources and generate electricity that can be put into the national grid to power our homes and businesses.
You can learn more about renewable energy on our Support Schools page or be reading through the information below:
Wind
How does a wind turbine work?
Westmill Wind Farm is home to five Siemens wind turbines. When wind turns the blades of the turbine, the generator inside of the nacelle (see diagram) is turned and this produces electrical energy, or electricity. This electricity is transported to the ground via cables running within the tower and into a transformer at the bottom which converts the electricity into a form which can be used in homes. The electricity then leaves the wind farm and is added to the local electric grid.
What wind speeds are required to produce energy?
The wind turbines begin producing energy when the wind speed at hub height reaches 3-5 meters per second (6-11 mph). Generally, the annual wind speed in Oxfordshire is 6.3 m/s.
The designed maximum power (i.e. the ideal wind speed to produce power safely) for the turbines at Westmill Wind Farm is 12 m/s (26 mph). At this wind speed, the turbines will generate 1.3 MW of electricity. Above 12 m/s, the wind turbines automatically reduce the amount of wind that they are catching by ‘feathering’ or turning the blades so less of the flat part can be pushed by the wind. This helps the turbine to maintain 1.3 MW generation. If wind speeds go above 24 m/s (55 mph), the turbines will turn into the wind and a parking brake will be applied to prevent damage to the turbines from spinning too quickly.
How are the turbines controlled?
At the top of each turbine’s nacelle hub is a weathervane which reads the direction of the wind. There is also an anemometer at the tail of the nacelle which measures the speed of the wind. A computer inside the turbine uses this data to turn the turbine as the wind shifts to ensure that the turbines are producing as much energy as possible. The computer would also apply the parking brake or take other actions to ensure that the turbines stay safe.
Solar
How does a solar panel work?
Solar panels are made up of photovoltaic (PV) cells, which are sandwiched between a number of other materials.
The sunlight that hits the solar panels is made up of lots of tiny particles called ‘photons’ which we can see as light. These photons can be absorbed by different materials and then transformed into types of energy, such as when the pavement becomes warm from the sun shining on it. In a solar panel, the top silicone layer absorbs the photons, exciting the electrons (microscopic particles charged with energy) in the cell. When excited by the sun’s photons, the electrons in the panel flow through its layers, creating a DC or direct current of electricity. DC energy can’t be used by homes, so an inverter changes the electricity into a usable AC, alternating current, so it can be used.
Does it have to be sunny for the panels to work?
No; solar panels do not need direct sunlight to produce energy. The panels need daylight rather than sunlight. Even on a cloudy day, the sun is emitting photons which can reach the panels and produce energy, although not as much as on a clear and sunny day.
The Co-op Model
Westmill Wind and Westmill Solar are both co-operatives. Members of the co-operatives receive a portion of the co-op’s revenue as an annual member interest payment. The Board of Directors, made up of, and voted in by, members, carries out roles that deliver specific support for the benefit of the co-operatives. At each annual AGM, members vote on aspects of the co-op such as member interest payments, community benefit grants and other motions put forward by the Board.
Directors of the Boards work with asset managers and operation and maintenance contractors to ensure proper management of the technologies at Westmill. They are also responsible for agreeing to new Power Purchase Agreements (PPAs) and other technical agreements.
As pioneering co-operatives in the community renewable energy movement, Westmill Solar Co-operative and Westmill Wind Farm Co-operative want to enable members to buy the electricity that we collectively generate. Currently, Westmill is able to offer members of either Westmill co-operative an annual Trading Dividend which gives them a discount on their electricity.
For more information on the co-operative model, please visit our About Us page.
Become a member
If you would like to learn more about joining one of our co-operatives, please contact us.
Generation
The Westmill co-operatives are committed to providing transparent information regarding current generation. We are currently working to present real-time data on the website. In the meantime you can see below our up-to-date generation figures for this year.
Who we sell to
The Westmill Wind and Westmill Solar boards are each responsible for negotiating new Power Purchase Agreements (PPAs). A PPA is a contract with an energy supplier for the price per unit (MWh) of electricity generated that is exported to the grid.
Westmill Wind and Westmill Solar both currently sell their energy to Octopus Energy, arranged through Younity.
