How do we harness different renewable energy sources?

Experts agree that microgrids are the future of renewable energy, and technology companies are ramping up their efforts to perfect these innovative systems.

Renewable energy has become an important topic in the past decade, with growing understanding and consensus on the reality of climate change. The need to provide low-carbon power matters now more than ever.

Harnessing energy from natural resources, such as the wind or sun, is a smart solution that helps reduce society’s reliance on fossil fuels. The increased use of energy from photovoltaic and wind-power plants, where power output can fluctuate depending upon weather conditions, has exacerbated the challenge of how to maintain energy availability.

"Reliable power supply – even during harsh weather conditions and times of peak consumption – is critical for economic growth"

Hence the growth in status of autonomous electricity networks, or microgrids. These are small-scale electric grids, which combine cogeneration plants, diesel- and gas-powered gensets (generator sets) and renewable sources, with batteries and a control system linking up all the elements. This intelligent energy-management system optimises the energy usage technically and economically.

Microgrids | Key facts

•    The global microgrid market is expected to grow from $22 billion (£16.9bn) in 2018 to $39bn (£30bn) by 2023

•    The Pacific island nation of Palau, the 13th-smallest country in the world, has committed to building the planet’s largest microgrid: 35MW of solar panels paired with 45 megawatt-hours of energy storage

•    North America is currently the largest microgrid market, having captured nearly half (49pc) of all vendor revenue activity

A microgrid – which can either function off-grid or connected to the main power grid – provides the overall control to coordinate these resources to meet the requirements of industrial, residential or consumer loads. Furthermore, microgrids enable a resilient power supply even with high penetration of intermittent renewable energy sources including wind and solar.

Localising power

“The concept of ‘island grids’ is very old. But in the new microgrids, renewable energies play a crucial role, and from a technical perspective microgrids are quite mature,” says Dr Peter Riegger, director of research and technology at Rolls-Royce Power Systems. “However, they are now entering more discussions because people are realising that – even in established huge national grids – microgrids bring many benefits. These include energy stabilisation and also levelling the cost of energy, due to the decentralisation driven by renewable energies.”

"At Rolls-Royce Power Systems, we are convinced that microgrids are the way towards a better use of energy"

Dr Riegger, based in Friedrichshafen – a city in southern Germany famed for its importance in aviation history – explains: “Formerly, the cheapest way to generate electricity was through a central power plant, and then having a grid and distribution across the country and countryside. Today it is much cleverer to integrate renewable energies at source.

“For example, here in south Germany, there is more sun than in the north, though in the north there is more wind. Integrating those fluctuating energies into local microgrids is much more efficient than having huge cables running from the north to the south.”

The ability of microgrids to separate themselves from the main grid seamlessly, in the event of a potential grid fault or emergency, is an increasingly important feature. Reliable power supply – even during harsh weather conditions and times of peak consumption – is critical for economic growth. As such, integrating renewable energy is a sustainable solution to support uninterrupted power as well as encourage clean energy use.

Huge savings

With the use of energy storage and renewable sources in a microgrid, industrial companies, operators of hotels, hospitals or schools and local communities are able to make significant fuel cost savings and at the same time protect the environment.

Microgrid solutions benefit utilities, industries and commercial sites that are looking for reliable power supply as well as cost and carbon emission reduction. Little wonder that, in early April, Rolls-Royce announced a global partnership with ABB on microgrid solutions that integrates digital technology and efficient hybrid power systems. The two organisations will offer an innovative, energy-efficient microgrid solution for utilities, commercial and industrial entities.

“At Rolls-Royce Power Systems, we are convinced that microgrids are the way towards a better use of energy,” Dr Riegger adds. “On our journey towards a decarbonised or carbon-neutral energy system, we need to integrate more renewables – but this only makes sense if you can optimise the local energy generation and the usage of electrical energy. It is, therefore, now absolutely necessary for people to embrace microgrid technology.”

How Rolls-Royce is leading by example with microgrid technology.

Rolls-Royce is currently building a microgrid that will serve its own site in Friedrichshafen, Germany. It can be operated either connected to the grid or in island mode.

The microgrid will also be used as a validation centre. This means that both in-house research and development programmes, as well as tests for potential or existing customers, can be run on the microgrid in a process of simulation and optimisation.

The microgrid currently comprises an MTU battery container with 1 MWh capacity, an MTU diesel genset and a gas-powered MTU cogeneration module, and is already in service delivering heat and electrical power to the site. In the next step, solar cells will be added.

Because the microgrid combines conventional and renewable energy sources and is controlled smartly, it is particularly attractive in terms of cost-effectiveness, reliability and eco-friendliness.

The generator sets will feed power to the microgrid whenever the renewable energy source – in this case sunlight for the solar cells – is inadequate or entirely absent.

Any surplus electrical power from the power plant or the solar cells will be stored in the battery container and can be used on demand. All the components are connected to each other via a smart energy management system, which optimises the way in which the energy is used both technically and commercially.

21 May 2019

THE TELEGRAPH