The 21st century demands change in energy generation and consumption across the globe. Since the industrial revolution, society has depended on fossil fuels for power, and the resultant emission of greenhouse gases and other pollutants has caused tremendous environmental degradation, rapid changes in climate patterns and loss of biodiversity. According to the Department of Business, Energy, and Industrial Strategy (BEIS), in 2016, the energy supply sector was responsible for 25% of the entire greenhouse gas emission in the United Kingdom, and as such the energy industry is at the forefront of criticism for its environmental practices. Energy has therefore been the first industry to undergo major systematic change as economies work towards a greener and more sustainable future.
Whilst the use of coal has been in decline for decades in developed economies (due to innovation such as centralised heating and the obsolescence of the steam engine), many nations have been actively phasing out coal and moving towards cleaner energy in the recent times. The United Kingdom is a prime example, where the share of coal in energy generation has fallen by over 10%, and the government has planned to phase it out completely by 2024. Similarly, Germany, which as of 2019 still uses 32% coal in its energy mix has planned to end coal-fired energy production by 2038.
Even the world’s two largest economies, the United States and China, have been observing a significant drop in the usage of coal. As per a report by Rhodium Group, an independent energy-research organization, the coal consumption in the United States dropped by a record 18% in 2019 driving a reduction of 2.1% in the overall GHG emission by the country.
As coal is phased out, alternative energy sources that are both cost-effective and clean must be implemented to pick up the slack. In the short run, natural gas is a strong contender due to its superior green credentials to coal, and gas plants’ flexible power output. Gas power releases approximately half as much CO2 per kWh as coal and a typical gas-powered plant is 42% efficient, compared to coal plant which is generally 33% efficient, meaning gas power plants are less wasteful. The UK is highly dependent on gas-fired power plants which are responsible for 41.94% of electricity generation, followed by renewables and nuclear energy which contribute 29.4% and 18.4% to its energy grid respectively.
The United Kingdom’s mix of renewable energy sources includes solar, wind, marine, hydroelectricity, and biomass. Biomass is a particularly strong contender to help cut out the UK’s remaining dependency on coal as it can be used in coal-fired power plants with minimal changes to infrastructure. For example, Drax power plant in the UK tested co-firing biomass mixed with coal for the first time in 2004 with a view to cut down CO2 emissions. Only after 15 years later, biomass has eclipsed coal as the primary energy source at Drax. Today the power plant’s capacity for biomass is 2.66 GW, which is more than double the plant’s capacity for coal.
The UK is visibly coming to grips with new methods of electricity generation, but the government’s continued investment in centralised energy plants is still being criticised.
A centralised energy system utilises large power plants for the generation and storage of energy, which is distributed via the national grid. By contrast, a decentralised system uses numerous smaller plants to generate electricity and power tends to be distributed directly to demand sites, or can be sent to the grid. This decentralised distribution is more cost-effective and eco-friendly than centralised power systems, which currently dominate the energy industry.
Decentralised generation (DG) can help us move towards sustainable power generation as it reduces issues associated with centralised generation (CG) such as excess electricity production, land usage, air pollutant emissions, and water usage & discharge. DG technologies can generate energy for both the residential and industrial sectors making use of renewable energy sources such as biofuels, solar, and wind. Decentralised generation can be particularly powerful in rural areas where combined heat and power (CHP) mechanisms can be run using regional natural resources such as wind and agricultural waste.
However, decentralised generation can also lead to certain negative environmental impacts. For example, DG plants that require combustion may be less thermodynamically efficient than the larger-scale centralised plants. Furthermore, CHP requires a large quantities of water for of steam generation and cooling, and although it raises overall efficiency, the electrical efficiency of CHP systems decreases, thus the purpose of a decentralised plant must be clear before construction and use, or you risk wasting energy.
Over the last few decades coal has been gradually phased out, and efforts to eliminate it from the energy sector continue. In the short term, an increase in the use of natural gas is likely, however the use of renewables such as solar, wind and biomass may eventually enable a completely green exit from coal. Decentralised power generation systems can also help us move away from coal, as they can utilise local natural resources for the generation of both heat and power. Although uptake is slow at present, the inherently less wasteful nature of decentralised generation may make a powerful addition to the power sector in the future.