Which Renewable Energy Source Can Produce Electricity And Heat Without Releasing Carbon Dioxide?

Introducing Renewable Energy

Which renewable energy source can produce electricity and heat without releasing carbon dioxide?

Renewable energy comes from natural sources or processes that are constantly replenished. Some examples of renewable energy sources are solar, wind, geothermal, hydropower, and biomass (U.S. Energy Information Administration, 2022). The demand for renewable energy is growing rapidly as countries seek to reduce carbon emissions and mitigate climate change. Global spending on renewable power capacity increased over 45% from 2010 to 2020, reaching over $300 billion (International Renewable Energy Agency, 2021).

Several factors are driving the increasing interest and demand for renewable energy worldwide:

  • Declining costs – The costs of renewable technologies like solar and wind have declined dramatically in recent years, making them more competitive with fossil fuels (Vantage Market Research, 2022).
  • Government policies – Many governments have implemented policies like tax credits, subsidies, and renewable portfolio standards to encourage the growth of renewables (Grand View Research, 2020).
  • Corporate procurement – Large corporations like Google, Apple, and Amazon are making major investments in renewables to power their operations and meet sustainability goals (SEIA, 2022).
  • Grid modernization – Upgrading to smart grids and energy storage options supports greater integration of variable renewables like solar and wind (NREL, 2021).
  • Job creation – Expanding renewable energy creates new jobs in manufacturing, construction, installation, and more. Solar jobs have grown over 250% in the last decade (E2, 2021).

With these drivers accelerating globally, renewables are positioned as a key solution for building sustainable and resilient energy systems.

Reducing Carbon Emissions

Human activities like burning fossil fuels for electricity, heat, and transportation have pumped excessive amounts of carbon dioxide into the atmosphere. According to CBS News, the world’s richest 1% produce double the carbon emissions of the poorest 50%. This disproportionate carbon footprint is accelerating climate change and its catastrophic impacts around the globe.

To avoid further temperature rises, sea level rise, biodiversity loss, and extreme weather events, we need urgent and aggressive cuts in carbon emissions. The Oxfam report highlighted that G20 nations are falling far short of their emissions reductions pledges and must take much bolder climate action. Phasing out fossil fuels, ramping up renewable energy, and making deep decarbonization across all sectors of the economy are essential steps to curb emissions and meet the Paris Agreement goals.

Hydroelectric Power

Hydroelectric power is generated by dams on rivers that use the gravitational force of falling or flowing water to turn turbines connected to electric generators. Hydroelectric dams have existed for over a century and can provide renewable electricity on a large scale. However, there has been debate around the emissions produced by hydroelectric reservoirs.

According to a 2017 study published in Science Direct, “Estimates of GHG emissions by hydroelectric reservoirs,” hydroelectric reservoirs emit greenhouse gases such as methane and carbon dioxide from the decay of flooded organic matter. While net emissions are typically lower than fossil fuel plants, they can still be substantial based on the size of the reservoir and other factors. The study found a mean emission rate of 5.36 gCO2/kWh across over 200 reservoirs analyzed (dos Santos, 2017).

Other analyses have found even higher emissions rates in some cases. A 2004 paper from UC Berkeley stated “hydroelectric reservoirs can emit greenhouse gases at rates comparable to fossil fuel power plants” with some emitting over 70 gCO2/kWh (Bock, 2004).

While hydroelectric energy is renewable and emits less lifecycle emissions than fossil fuels, reservoir emissions are an important consideration when evaluating its climate impact compared to other renewable sources.

Wind Power

Wind power harnesses the wind to generate electricity using wind turbines. Wind turbines convert the kinetic energy from wind into mechanical power to drive electric generators (Lehman, 2011). Typically, wind turbines are grouped together into wind farms that contain dozens or hundreds of individual wind turbines.

Wind power capacity and the number of wind farms have grown substantially over the last decade. According to RenewableUK, wind power generation in the UK grew from 1.5GW in 2000 to over 13GW in 2015. The UK is now home to more offshore wind power capacity than the rest of the world combined (LexisNexis, 2015).

Solar Power

Solar panels have seen tremendous growth in the residential and commercial sectors due to falling costs and improved efficiency. Between 2010 and 2019, the average cost of solar panels fell by 82% (from $7.50/watt to $1.35/watt), making solar energy cost-competitive with fossil fuels in many markets (Source: https://www.linkedin.com/pulse/space-based-solar-power-market-detailed-tejne/)

Solar panel installations have accelerated rapidly as prices have declined. An estimated total of 121 GWdc of solar PV capacity was installed globally in 2019, a 23% year-over-year increase. The residential solar market in the United States grew 19% in 2019 alone. Major markets like California and Texas are approaching 2 million solar installations on homes. (Source: https://danieldavenport.medium.com/the-momentum-of-the-solar-energy-transition-implications-for-electric-vehicles-and-transportation-b7b741de1cba)

The continuing fall in solar panel pricing along with supportive government policies have made solar power generation competitive with fossil fuel plants in most major markets. This has unleashed massive demand from both homeowners wanting to go solar and from large-scale utility projects. The next decade should see solar become a major chunk of electricity generation globally.

Geothermal Energy

Geothermal energy harnesses heat from beneath the earth’s surface to generate electricity and provide heating and cooling. The word “geo” means earth, and “thermal” means heat, so geothermal energy is literally “earth heat.”

Geothermal energy relies on the heat within the earth’s core, where temperatures can reach over 9,000 degrees Fahrenheit. This heat emanates outwards towards the surface. Normally this heat dissipates, but in some areas known as hydrothermal sites, subsurface water absorbs the heat and carries it towards the surface as hot water or steam. Wells can be drilled into these hydrothermal reservoirs to tap the heated water or steam, which rises to the surface and emerges as hot springs or geysers. This fluid can be harnessed and drawn through the wells as hot water or steam to generate electricity at the surface without combustion or carbon emissions.

To generate electricity, the geothermal fluid is piped up through production wells to power plant facilities on the surface. The hot fluid vaporizes a liquid to drive turbine generators, which then produce electricity. Cooled fluid is returned to the reservoir through injection wells, completing the loop. Geothermal power plants run steadily 24/7, unaffected by weather conditions.

Biomass Energy

Biomass energy comes from plant and animal material. Sources of biomass include wood, crops, sewage, and animal manure. The organic matter is burned to produce heat and generate electricity. Many people believe biomass is a carbon neutral energy source because the plant material absorbs carbon dioxide as it grows. When burned, it releases the same amount of carbon into the atmosphere. However, some argue biomass is not entirely carbon neutral.

According to a 2022 study, biomass fuels are not carbon neutral in principle because burning biomass releases carbon back into the atmosphere that would otherwise remain stored (https://www.mdpi.com/1996-1073/15/24/9619). The Biomass Library FAQ also states biomass is not carbon neutral, as burning biomass releases CO2 and it can take decades for new plant growth to re-absorb that carbon (https://environmentalpaper.org/biomass/biomass-faq/). Despite this debate, biomass energy is still considered renewable and cleaner than fossil fuels. Using sustainable forestry practices can help maintain carbon neutrality of biomass energy.

Comparing Renewable Options

There are a variety of renewable energy sources available today that can produce electricity without emitting carbon dioxide, each with their own advantages and disadvantages in terms of cost, scalability, and resource availability. Key options to compare include:

Solar power harnesses energy from the sun using photovoltaic panels or concentrated solar thermal plants. Solar energy can be deployed on both small and utility scales. The cost of solar has declined dramatically in the past decade, making it cost competitive with fossil fuels in many markets. However, solar power is intermittent and limited to daylight hours. Energy storage or backup power is needed to provide electricity when the sun isn’t shining.

Wind power captures the kinetic energy of wind using large turbines, and converts it into electricity. Wind power scales from single turbines to multi-megawatt wind farms. The cost of wind power has also declined substantially, but output depends on having adequate wind resources. Offshore wind farms can provide more consistent power but at higher costs. Like solar, energy storage is needed to provide power when the wind is not blowing.

Hydropower harnesses the energy of flowing water by sending it through turbines in dams. Hydropower provides consistent baseload power but requires suitable geography and naturally flowing water. Most good sites for large hydro dams have already been utilized in developed countries. Smaller run-of-river and micro hydro projects have less environmental impact but also provide less power.

Geothermal power utilizes heat from under the earth’s crust to produce steam to turn turbines. Geothermal provides constant power but has only limited geographic availability as it depends on subterranean heat sources. Enhanced geothermal systems can broaden potential by pumping water underground but increases costs. Direct use of geothermal heat can provide heating and cooling in addition to electricity generation.

Each renewable energy source has pros and cons in terms of availability, cost, environmental impact and ability to provide consistent power. Integrating a diverse mix of renewables along with energy storage and transmission can overcome intermittency issues and provide carbon-free energy.

Overcoming Renewable Challenges

While renewable energy sources like solar, wind, hydroelectric and geothermal offer many benefits, they also come with unique challenges that must be addressed for large-scale implementation. Three key challenges involve intermittency, storage and transmission (cite: https://sustainablereview.com/challenges-in-renewable-energy/).

The intermittency of renewable sources like solar and wind poses reliability issues for energy grids. Power output depends on weather conditions and time of day, which can cause unpredictable fluctuations. Solutions involve improving forecasts to anticipate variation, increasing grid flexibility to balance supply and demand, and diversifying sources across larger geographic areas (cite: https://www.sap.com/insights/renewable-energy-challenges.html).

Affordable and scalable energy storage is also needed to capture excess renewable power when available and discharge it when needed. Promising storage technologies include pumped hydro storage, compressed air storage, flywheels and advanced batteries, but continued innovation is required for widespread adoption (cite: https://www.trvst.world/renewable-energy/challenges-for-renewable-energy/).

Finally, transmission infrastructure must be enhanced to deliver renewable energy from source to demand centers. This involves expanding long-distance, high-voltage transmission lines and developing smart grid capabilities to dynamically optimize power distribution in real-time based on supply and usage data.

The Renewable Future

The growth potential for renewable energy is enormous. Solar and wind power are projected to see massive expansion by 2050, with solar potentially providing up to 35% of global electricity by 2030 according to projections by the International Renewable Energy Agency (IRENA) The Growth of Renewable Energy: What Does the Future Hold?. Onshore wind capacity could increase 57% by 2024 The Growth of Renewable Energy: What Does the Future Hold?.

To fully transition to renewable energy and curb the worst impacts of climate change, massive investments in renewable infrastructure and grid modernization will be needed globally. But the potential is there if the political and collective will can be mobilized to make it happen. The present decade is crucial for getting policies and incentives aligned to accelerate the transition before it’s too late. The future is renewable if we act now to make it happen.

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