Virtual Power Plants: What are they and what are their advantages for renewable technology?
Renewable energy has come a long way in the past few years, especially in Northern Ireland, with the country exceeding its 2020 target of 40% electricity supply coming from renewable sources in June of last year. The large majority of our renewable energy capacity here in Northern Ireland comes from wind, accounting for approximately 85% of the renewable mix. As we continue to reach for the ultimate goal of complete reliance on renewable energy sources, we must think about how we will overcome the biggest challenges associated with creating this new energy infrastructure. One of the biggest challenges is, of course, the intermittency of most renewable energy sources. In order for a country or population to be completely reliant on renewable sources for electricity, we would need a system that could overcome this problem of intermittency and meet the demand of power consumption on a 24/7 basis. This is where virtual power plants may come into play.
What are they?
Virtual power plants (VPPs) and virtual power stations (VPSs) refer to the same concept that has been described as an “internet of energy”. A VPP can be broken down into a number of different elements which allow for the coming together of numerous independent renewable energy generators to create one big power plant which is controlled by a single central control system. The “virtual” element of the concept is due to the multiple renewable energy generators being controlled remotely. The best way to explain how a VPP works is to look at an example that is already operating.
The biggest VPP currently running in Europe is operated by the Norweigan company Statkraft, with the plant itself being based in Germany. This VPP connects the electrical output of around 1,400 independent power producers, giving an overall joined capacity of over 10,000MW. These power producers include 1,300 wind farms, 100 solar units and a number of hydropower and bioenergy generators. Figure (below) shows the general bias of their VPP. Each renewable energy generator involved in the VPP is connected to a remote-controlled unit or has an inbuilt connection to the central control centre. This unit allows for that independent generator to be controlled by the plant's central control centre. This connection also allows for bi-directional exchange of data, meaning the central control centre can receive information about the generator's current capacity and power output while the generator itself receives information regarding whether it should start up, or shut down, or increase or decrease power output at any given time. The control centre itself acts as a huge database, collecting information on all the various renewable energy generators, whilst also monitoring market prices, analysing weather forecasts and creating production forecasts. The centre uses all of this data to then operate each individual generator in a way that both maximises profits for the generators and keeps energy prices low for energy consumers.
What are its advantages?
Another big VPP currently operating in Europe is operated by the German company Next Kraftwerke. The company's VPP connects renewable generators of hydropower, biogas, solar and energy storage systems which collectively has a network capacity of 7,560MW. As mentioned, their VPP operates by connecting to each renewable generator through a remote 'next box' which allows for the exchange of data and operational commands. Kraftwerke's control system then compiles all of its data from the generators, the grid, it's energy storage system, market prices and production forecasts which allows for the following:
- Using prediction forecasts, generators that are not affected by an up and coming weather change are ramped up while those generators that may be affected are ramped down or shut off e.g. if the forecast prediction is signalling cloud coverage over a solar farm, the control system will ramp up the power output of bioenergy plants in order to maintain overall output and balance intermittency problems.
- Use excess renewable energy to create hydrogen and store this gas until it is needed within the gas network for heat demand.
- Increase independent generator capacity during peak loads.
- Using market prices, the control system can create optimised price schedules which ramp up or down flexible power consumers (like an industrial pump) which allow for the consumption of electricity when it is cheap and demand is low.
- Control of flexible power generators such as bioenergy plants and hydropower plants which allow for grid frequency control and general balancing services for the grid.
These current VPPs are currently showing real promise in terms of paving the way for a decentralised energy system. It is evident that the problem of intermittency can be resolved with the use of complex algorithms and the coming together of independent generators, but it is also evident that this new internet of energy has many advantages which benefit grid operators, power producers and power consumers collectively.
Progress in the UK and Ireland
Since last November, Statkraft has been involved in the UK's 'balancing mechanism' in the South-West of England. The company has been using a gas generating network of 20MW capacity alongside its software and algorithms to help the integration of renewable energy capacity into the grid within the area, as well as help with grid stabilising needs.
Centrica, the international energy services provider, has teamed up with an innovative battery company, Sonnen, to create an advanced VPP within the UK that has been operating for the past 12 months. Through the installation of 100 domestic batteries in UK homes that have been connected to the grid, a network of decentralised home energy storage has been created. The network acts as a cloud platform which allows storage space to be sold when the grid is overloaded and allows energy to be released during times of peak loading. This cloud-based storage system not only helps relieve the grid but also allows homeowners with solar PV installations to make the most of their generation which in turn minimises their energy bills.
Another battery company, originating from London, Moixa has set about VPP progress in both the UK and Ireland. Within the UK, the company has plans for a 3-year project, which started last year, and aims to build up to a 17MW capacity of connected solar PV, electric vehicles and battery storage. Moixa's main goal of the project is to demonstrate the benefits of linking heat, power and transport in one local system. Within Ireland, Moixa has teamed up with Irish energy provider, Energia, to develop a VPP involving domestic battery storage and electric vehicle charging points to provide frequency-related grid services to the Irish transmission operator, EirGrid.
The future of VPPs looks very promising and they may even bring us closer to our ultimate goal of complete decarbonisation within the energy sector. If you'd like to read more on decarbonisation, you can check out our interview with B9's David Surplus.