Microgrids, a micro-universe
A microgrid is a local energy system that can operate both within a centralised system and autonomously – on its own – if required.
It is a self-sufficient energy system that serves a specific area or site – a hospital or business centre or a district or island.
A standard centralised network brings homes or buildings together with a single source of energy. An accident at a power station, depending on its scale, can leave several homes or buildings without power – or entire districts.
A microgrid is a smaller copy of a centralised network able to supply power to consumers on the basis of its own generating sources. This means that at any time they can switch off from the centralised supply and keep on working by generating their own electricity.
One or several sources of energy operate within the micro-network – solar panels, wind turbines, combined production of heat and power, generators. Many new micro systems include stored energy (generally batteries) and now, chargers for electric vehicles.
Micro-networks provide consumers with power – and heat, if necessary – on the basis of complex programmed supply and operating systems.
Smart microgrid systems are able to switch independently from one energy source to another, use both sources at the same time or even all sources at once. Even if one station goes off line, other sources will come on stream and the consumer will notice nothing as power supplies continue uninterrupted.
Centralisation: the problems
The first microgrids came into use at the end of the 19th century as Thomas Edison’s so-called electric systems. They amounted to an electric generator and a small local network – enough to supply a house with outbuildings or several private homes. Only people of means were in a position to acquire such a system.
That prompted Edison to come up with the idea of building the first commercial station on Manhattan that supplied power to several workplaces and kept the buildings heated.
And that is how the General Electric company started.
Years later, the problems of large centralised electricity networks became apparent.
Large centralised networks that to this day supply most power in the world and move it from power stations over vast distances on power and distribution lines.
One of the most significant disadvantages of centralised system is that, once generated and sent to the consumer, the power must be used immediately. Academics are working on the problem of energy storage, but so far have not solved it in the necessary commercial scale. And not to be forgotten is the loss of eight to 15% of electricity in the process of transmission.
Centralised systems have not always proven to be wholly stable in the face of natural disasters and other extraordinary circumstances. Interruption of their operations can lead to large numbers of consumers losing their power, including factories and socially important sites. And in the world of today, even a minute of power interruption could bring about multi-million dollar losses for business.
And back-up systems for centralised energy networks in remote, difficult-of-access, thinly-populated areas have generally proved to be economically unfeasible.
Centralised systems are less dynamic in that they do not always react promptly to daily or hourly leaps in demand for electricity
And as small generators and other equipment become more readily available using solar or wind power, a new class of electricity consumer has emerged – a consumer that can be a market supplier at the same time.
As a result, a need has arisen for new types of local energy networks using a variety of energy sources, some of them independent or autonomous in nature.
One of the first experts to work on the concept of micro-networks and smart energy networks was Greek academic Nikolaos Hatziargyriou.
Hatziargyriou set up Europe’s first micro network on the small Greek island of Kythnos – working entirely from solar and storage batteries with a smart system taking account of fluctuations in energy consumption and production.
And so the term “microgrid” was born. This year, Hatziargyriou was awarded the “Global Energy” prize for his work in this field.
Stable and smart systems
One of the problems tackled by microgrids for modern energy networks is stable supply and control of power in difficult-of-access areas. The micro network provides energy for nearby consumers, solving the problem of ineffective supplies and energy loss. The generators are located right next door, inside a building or – in the case of solar batteries – on the building’s roof or walls.
The microgrid can switch itself off from the central network and work independently, supplying energy direct to consumers In the event of a hurricane, snowstorm, fire or earthquake.
Such systems are of particular interest in the United States, where the central network is huge and has no reserve capacity system (as is the case in Russia, for instance) which leaves it vulnerable and subject to frequent power cuts. Seven years ago, a branch falling on a power line shut off transmission to several states and even Canada was affected.
Microgrids enable the system to avoid cascade shutdowns as specific sections of the network can be served in isolation. They also eliminate additional costs associated with reserve capacity.
Modern microgrids have micro networks subject to a controller. This is essentially the “brain” of the system which directs the generators, batteries and highly complex adjacent energy systems. Through this controller, consumers can work with the lowest prices, raise the level they use of clean energy and achieve maximum reliability of their power supply.
The controller is able to keep track in real time changes in wholesale power prices in a centralised network and, should these decrease, step in to buy energy for its customers. Energy received from its own sources (like solar panels) can be sent to battery chargers for storage. If the price of power from the central network rises, the system allows for a “decoupling” from the system in order to use accumulated reserves of power.
Micro-networks can also produce heat, in addition to power.
And microgrids are becoming “smarter” by the minute.
Not only do they simply advise energy networks of consumer demand, they allow for energy consumption to be regulated in relation to the level of supply at any given moment. And that is why officials in the United States are examining ways of promoting the use of microgrids as they allow for greater stability in the operation of the entire energy system.
Range of use
The American market is one of the biggest for microgrids in the world.
In 2018, the total number of microgrids stood at 2,250. And in 2019, a record number were set up – 546, with most having a capacity of up to 5 megawatts. The trend in recent years is clear – smaller, more mobile projects are undergoing growth. They attract more and more investments against a background of lower costs and reduced time needed to install them.
The research and consulting group Wood Mackenzie predicts that the number of private investors in this sphere will rise at the expense of other market participants, including those in the oil and gas sector.
For instance, the “Smart Neighbor” project in the state of Alabama includes solar panels, lithium ion batteries and gas turbines – all belonging to a single cooperative and centrally controlled with air conditioning and ventilation systems. There are sufficient battery reserves for 12 hours.
In Houston, a unique microgrid will come into service in 2022 aimed at stabilising power supplies to a water purification plant. This will be the largest micro-network in the country to ensure the operation of a water pumping station – and it will operate on gas.
A similar network is under construction in California at the municipal wastewater treatment plant in Hiller Park. The microgrid will use an existing diesel generating system and new solar photovoltaic and battery energy storage facilities.
Research conducted by the international consulting firm Deloitte showed that 44 % of businesses in the United States are studying the possible use of microgrids. And more than half of those companies carry out operations for which a stable power supply is of critical importance.
More than half the business representatives polled expressed concern at the growing number of power outages for reasons that included hurricanes, fires and accidents. A total of 37 % of rank-and-file citizens surveys expressed similar concerns.
Of businesses surveyed 10 years ago, 20 % of companies had some form of their own generation. That number has since risen to 60 %. And more than half the businesses said they were working on ways of boosting the share of the power they use from renewable sources.
Micronetworks are used in all sectors, but the trailblazers here were data centres, family farms, electric vehicles, university campuses and military sites. Micronetworks were also popular at ports and in mining companies.
According to Wood Mackenzie consultants, in 2019, a total of 86 % of capacity of micronetworks’ installed capacity was provided by fossil fuel production. But by 2025, solar, wind, hydroelectric power and stored energy will account for 35 % of capacity brought on stream per year.
It should nonetheless not be forgotten that the main aim of microgrids is to ensure reliability and the optimal systems used are combinations of renewable resources, gas and diesel fuel.
But analysts also point out that the COVID-19 pandemic has had an effect on this sector. In the first six months of 2020, the rate of growth in microgrids was the slowest over the past four years owing to uncertainty among investors or unwillingness to proceed with large investments.
By Alyona Zhuravlyova, Global Energy Observer.