Distributed generation

Electricity can be produced through two very different methods. Most of our power comes from centralized generation. This method uses massive power stations to create bulk electricity. These stations might use coal, natural gas, or nuclear energy. They also include large hydroelectric dams and massive solar farms. Because these plants are so large, they are often built far from cities. For example, coal plants are built near mines to save on transport costs. Hydroelectric plants must be located where there is enough water flow. This electricity then travels over long distances through a massive transmission and distribution grid.

Distributed generation offers a different approach to powering our lives. This method uses small, modular devices called distributed energy resources, or DERs. These devices are located very close to the people or buildings that use the power. A DER system typically has a capacity of 10 megawatts (MW) or less. Some systems use multiple different parts to work together. When they combine different types of energy and storage, they are called hybrid power systems. These systems can be grid-connected or even function as part of a local microgrid.

Distributed energy resources use many different types of fuel and technology. Many DERs rely on renewable energy sources. These include solar power, wind power, and geothermal power. They can also use small-scale hydro, biomass, or biogas. Some systems use natural gas through processes like cogeneration. Cogeneration, or combined heat and power (CHP), uses steam turbines or engines to make electricity. It also captures the hot exhaust to provide heat for water or buildings. Some advanced systems even use that heat to provide cooling through an absorptive chiller.

Historically, the world relied almost entirely on large central plants. It was much cheaper to build one giant facility than many small ones. However, this changed around the late 1960s. By the start of the 21st century, central plants faced new challenges. The long-distance grid was aging and sometimes caused power quality issues. Digital equipment requires extremely reliable electricity to function correctly. Experts found that making small units in large amounts was becoming very efficient. This is known as the economy of mass production.

Distributed generation provides several important benefits to the energy system. One major benefit is efficiency. When electricity is generated in the same building where it is used, very little energy is lost. In centralized systems, energy is lost as it travels over long power lines. Distributed systems also help the environment. They often use clean, renewable energy instead of fossil fuels. This can reduce the total amount of carbon emitted. Another benefit is security. If the main power grid has a problem, a microgrid can disconnect and operate autonomously. This helps keep the lights on during a disturbance.

There are specific technologies that make these systems work. Photovoltaic systems, or solar PV, use solar cells to turn sunlight into electricity. Fuel cells are another important tool. In 2012, Japan's Ene Farm project sold 20,000 fuel cell units. These PEM fuel cell units have a lifetime of about 60,000 hours. This means they can last between ten and fifteen years. Other technologies include microturbines, reciprocating engines, and small wind power systems. Some people even combine solar, fuel cells, and batteries to power a single home.

While the benefits are many, integrating these resources is complex. Because wind and solar depend on the weather, their output is uncertain. This makes it harder to balance the supply of power with the demand. It can also put pressure on the transmission network. Sometimes, it even causes "reverse power flow" from the local system back to the main grid. There are also cybersecurity concerns. If many small devices use the same control software, a single attacker could potentially disable them. This is why new rules, like the EU NIS2 directive, are being created to protect energy systems.

Finally, we can look at the concept of grid parity. Grid parity happens when an energy source becomes as cheap as the electricity from the main grid. When a technology reaches grid parity, it does not need government subsidies to grow. Since the 2010s, solar and wind power have reached grid parity in many places. This includes parts of the United States, Europe, and Australia. As technology improves and more people use it, the costs continue to fall. This makes distributed generation a key part of a diverse and clean energy future.