Is Renewable Energy Efficient? (Solar, Wind, Hydro, Geothermal & More)

Is Renewable Energy Efficient? (Solar, Wind, Hydro, Geothermal & More)

There’s a few different ways you can look at the efficiency of renewable energy.

In this guide, we outline how efficient renewable energy might be across those different areas.

 

Summary – Efficiency Of Renewable Energy

  • Renewables tend to keep much more of their original energy input than fossil fuels, and in many cases produce more energy than the input amount (i.e. if efficiency is over 100%)
  • Much of this has to do with the fact that renewables don’t require a lot of the extraction and refinement processes (where energy is lost and there is waste) like fossil fuels do
  • The energy footprint for renewables really only comes from production, and any waste produced
  • In addition, renewables don’t require the use of energy to mitigate or address environmental and social problems like fossil fuels do
  • Biomass and bioenergy might be one of the exceptions to the above generalisations, as biomass and bioenergy does involve refining and processing with some types energy conversion (biocrops and biofuels are good examples)
  • Efficiency numbers and %’s are usually provided as a national average, but can also vary from State to State depending on different variables and factors with different renewable energy sources
  • Other analysis’ of energy efficiency mention that we have to take into account theoretical maximum efficiency, and the capacity factor of different energy sources. We also have to consider how each energy source operates in reality in a real energy system and power grid when other energy sources are also providing power to a grid. Economically, when we take into account these factors and consider efficiency, renewables still come out ahead because they don’t even have to be efficient … they just have to run enough over the course of time to pay for their capital costs … whereas the marginal operating costs of fossil fuels should place pressure on them to be efficient.

 

How Efficient Is Solar Energy?

In the US, as a % of energy input retained when converting fuel to electricity:

  • Solar creates 207% of it’s original energy 

– hortidaily.com

 

How Efficient Is Wind Energy?

In the US, as a % of energy input retained when converting fuel to electricity:

  • Wind creates 1164% of it’s original energy 

– hortidaily.com

 

How Efficient Is Hydro Energy?

In the US, as a % of energy input retained when converting fuel to electricity:

  • Hydro creates 317% of it’s original energy 

– hortidaily.com

 

How Efficient Is Geothermal Energy?

In the US, as a % of energy input retained when converting fuel to electricity:

  • Geothermal creates 514% of it’s original energy 

– hortidaily.com

 

How Efficient Is Biomass?

In the US, as a % of energy input retained when converting fuel to electricity:

  • Biomass retains 29% of it’s original energy 

– hortidaily.com

 

How Efficient Are Tidal & Wave Energy?

*We currently don’t have stats for tidal and wave energy.

But, woodharbinger.com says this about tidal energy:

  • [tidal energy] … is more efficient than wind energy due to the density of water and more efficient than solar energy due to its high ~80% conversion efficiency

 

Why Is Renewable Energy So Efficient Compared To Fossil Fuels?

From the above numbers, we can see that renewable energy is generally more efficient than fossil fuels. 

As described by Vox.com, renewable energy is generally more efficient across all three of the electricity, transport and heating/cooling sectors:

  • Renewable electricity … is simpler [across the entire process to get to the stage to deliver electricity]. It involves no combustion and fewer conversions [than the fossil fuel conversion process] generally.
  • … Electric motors are simpler than combustion engines, with fewer moving parts, substantially lower maintenance costs, and much higher efficiency.
  • … Electrified heating and transportation sectors can be integrated into electricity grid operations, creating system efficiencies

 

Efficiency Can Actually Vary From Place To Place (Depending On Different Variables)

There can be variables to energy efficiency in different States and cities, such as how direct the sunlight is, what renewable technology is used, infrastructure used, plus other factors that can impact the final efficiency number of an energy source or method.

So, the above numbers are averages, rather than State or city specific averages/numbers.

 

How Energy Source Efficiency Numbers Are Calculated

Something that should be noted is that the numbers are based on economic efficiency:

  • Hortidaily.com explains the methodology of calculating the averages in their resource 

Borntoengineer.com also has some information on how to measure the efficiency of an energy generation method.

 

Some Other Notes On The Efficiency Of Energy Sources

Paraphrased and summarised from Michael Barnard on Quora.com, reappearing on Forbes.com:

  • Fossil fuel has to be paid for, where as the sun and wind are provided by nature for free
  • ‘Efficiency is explicitly a measurement of how much of a given resource’s energy potential gets turned into electricity’
  • ‘Solar turns around 20% of it’s energy potential into electricity’ [but the other 80% that is wasted is not expensive and is not really even a waste]
  • ‘Car engines only turn about 20% of the energy in gas into movement, with the rest being waste heat.’
  • ‘Coal plants achieve from 33% to 40% efficiency in the best cases, with the rest being just wasted heat.’
  • ‘Combined cycle gas plants, where the heat is used in addition to the mechanical energy to generate electricity manage to make it up to about 54% efficiency’
  • … with fossil fuels … we are paying for 100% of it plus the costs associated with addressing carbon emissions and other externalities … so it’s ‘arguable that we are paying for 300% of the fuel but only getting 20% to 50% out of it’
  • Each energy source has a Betz’ Limit theoretical maximum efficiency, and the theoretical maximum efficiency of wind energy isn’t that different from a combined cycle gas plant
  • … but, maximum efficiency has to be combined with the capacity factor (how much capacity for energy generation an energy source has in a given year) to determine the electricity generation potential of an energy source
  • Solar capacity factor ranges from 15% to 25%, and modern wind farms range from 40% for onshore to 77% one year for the best offshore site
  • In a real energy grid – renewable energy can be curtailed because they have to exist with nuclear and other baseload forms of generation can’t be turned down quickly
  • Nuclear and other baseload energy sources tend to have worse economics
  • Traditional/legacy forms of electricity generation tend to have low capacity factors … ‘Nuclear is high at 90% because it can’t actually run at less than that capacity factor and pay for itself’ … ‘Coal in the USA was at 60% or so a decade ago, but now it’s at 50% for the country because wind, solar and gas are cheaper so it can’t compete. Many gas plants are at 10% simply because they only turn them on to provide peak power at highest profit’
  • ‘So wind and solar don’t have to be efficient, they just have to run enough over the course of time to pay for their capital costs. Their marginal operating costs are dirt cheap, much cheaper than coal and gas plants.’

 

Sources

1. https://www.bettermeetsreality.com/renewable-energy-vs-fossil-fuels-vs-nuclear-comparison-guide/

2. https://www.hortidaily.com/article/6011458/us-what-is-the-most-efficient-source-of-electricity/

3. https://www.vox.com/energy-and-environment/2019/6/18/18681591/renewable-energy-china-solar-pv-jobs

4. https://www.bettermeetsreality.com/are-fossil-fuels-efficient-coal-oil-natural-gas/

5. https://www.woodharbinger.com/tidal-energy-sustainable-resource/

6. https://www.borntoengineer.com/efficient-form-renewable-energy

7. https://www.forbes.com/sites/quora/2017/11/08/is-solar-energy-less-efficient-than-non-renewables/#7f8b511f4d4a

8. https://www.quora.com/If-solar-energy-is-inefficient-then-how-do-solar-energy-organizations-sell-their-products

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