Rising energy demands, decaying infrastructures, and a shift in public attitudes in favor of more sustainability are transforming the energy market and injecting pace into the energy turnaround. Accompanying the rise of regenerative energy sources is the growing trend towards microgrids, which integrate low-cost, ecological renewables with stable forms of power generation such as diesel- and gas-powered generator sets.
Microgrids are small power grids that combine electricity from decentralized energy generation sources such as combined heat and power plants, diesel- and gas-powered generators, and renewable energies with batteries. A microgrid control system coordinates the energy sources in order to provide the energy required for industry, residential buildings or commerce accordingly.
It's a small, unremarkable construction recently put up by Rolls-Royce on mtu Plant 1 – with solar panels on the roof, air gratings for windows, and alongside it a grey 40-foot container. But it houses something very special – the company's brand new microgrid Validation Center with proprietary microgrid.
Inside are special transformers, inverters and switchgear that simulate the function of energy sources such as wind and hydropower that a microgrid can also integrate. The heart of the system is the 40-ft mtu battery container standing outside that provides the flexibility needed to use the different energy sources. In the Friedrichshafen setup, these are photovoltaic collectors on the roof of the Validation Center and a factory building delivering a total of 500 kW peak power, a combined heat and power module based on mtu gas engines, and an mtu diesel generator set. A smart controller developed in-house ensures optimal energy deployment by determining when it is most economical to use which energy source for feeding to consumers or charging the battery. The consumers in this case are the factories and an office building. “Our top priority is always to ensure the stability of the power supply so that there are no interruptions to our production operations,” explained Armin Fürderer, who, along with a team of colleagues, was responsible for the conceptual design and construction of the new energy system. Another objective is to provide electrical power that is as green, clean and cheap as possible, enabling for example, several hundred tons of CO2 emissions to be cut each year. In addition, the combined heat and power module delivers heat which can either be used directly on site or as district heating for local homes. Overall, 4.8 MW of electrical power and 1.5 MW of thermal output are available for the company's on-site operations.
“This is a very interesting proposition for operators from all branches of industry, because they can either improve the capacity factor of their existing power installation or use the microgrid as a stable or autonomous source of power”
Islanded or grid-connected
As the potential for using renewable energies grows, so does the challenge of storing the surplus energy produced by photovoltaic cells and wind turbines to be used as and when required. Another challenge is compensating the weather-induced fluctuations that the use of renewables inevitably involves. Microgrids meet both those challenges by connecting the sources of electrical power to batteries and a control system and integrating all elements by means of smart energy management that determines which type of energy can be optimally harnessed and when. This makes for a stable source of power that allows operators to loosen their dependency on the public grid or become fully autonomous. “This is a very interesting proposition for operators from all branches of industry, because they can either improve the capacity factor of their existing power installation or use the microgrid as a stable or autonomous source of power,” explained Fürderer. Such operators can be public utility companies already running CHP modules and photovoltaic installations, largescale farms with biogas plants that likewise use solar and wind power, or businesses that want to free themselves from the public grid.
Individual microgrid simulations at the mtu Validation Center
Irrespective of whether the customer wishes to improve capacity utilization of their existing installations or integrate them better, or is looking for a brand-new microgrid suited to their local conditions, the Validation Center is at their service: “In our Validation Center, we can configure microgrids of various sizes, capacities and layouts and demonstrate to the customer how they will function – also taking into account the wind and sun conditions that prevail at the customer's location,” said Fürderer. What takes place is not a computer simulation, but a realistic replication of an individually configured microgrid using high-tech components.
The Validation Center capabilities reflect the comprehensiveness of the mtu microgrid portfolio, which covers battery capacities from 50 kWh, enough for around 50 washing machine cycles, to 2 MWh, equivalent to the yearly power requirement of a single-person household. “Microgrids are almost freely scalable, and you can increase their capacity by using, for example, several battery containers, a bigger photovoltaic installation, or by adding on wind turbines and larger or extra generator sets,” added Fürderer.
New products to facilitate a single-source solution
Since microgrid solutions comprise not only traditional mtu products such as diesel- and gaspowered generator sets, but also batteries and controllers, Rolls-Royce Power Systems decided to broaden its portfolio, and duly launched its new mtu EnergyPack on the market in January 2019. Electrical power generated from the various sources is stored in the 40-ft battery container and can be made available at the push of a button. The battery container was developed in-house at Rolls-Royce Power Systems and comprises 154 modules with 3,388 lithium-ion cells. These can store just under 1,000 kWh of electrical power – 14 times as much as a Tesla Model X. In cooperation with the start-up Qinous, in which Rolls-Royce Power Systems has acquired a majority stake and renamed Rolls-Royce Solutions Berlin, the existing product portfolio is being harmonised and further developed. Rolls-Royce Solutions Berlin has already gained experience on more than 30 projects worldwide in the integration of battery storage and energy systems into microgrids and has also integrated mtu systems from Rolls-Royce.
US installs own solution
Rolls-Royce has set up another proprietary microgrid at its mtu facility in Aiken, South Carolina (USA). In the short term, this microgrid is demonstrating “islanding” operation by powering a section of the facility using renewable energy sources, completely independent of the public grid. In the long term, it will demonstrate the peak-shaving concept by reducing the plant's electrical peak power demand from the utility and help reduce its dependency on public grid. The site is taking advantage of South Carolina’s abundant sunshine with 1 MW capacity of solar panels, many of them installed atop covered employee car parking. The solar array is synchronized with a 1MWh mtu EnergyPack battery system and a microgrid controller. Additionally, a 1.9 MW diesel generator set serves as a backup to the whole microgrid system. The microgrid provides easy access to customers onsite who are interested in a demonstration. The US microgrid is up and running since end-2020.