Solar energy is rapidly becoming the energy generation choice worldwide. In 2019 solar energy installations represented nearly 50% of all new energy-generating plants constructed. New natural gas and coal generation plants accounted for 12% and 7% in the same year. Over the last 2 years, Alberta had invested billions in solar energy systems. While countless institutions, businesses and governments are investing in solar energy, critics are quick to point out that the efficiency of solar energy (20%) is lower than gas turbines (40%); much lower than combined-cycle gas turbines (80%).
So why are we investing so much into a lower-efficiency technology?
The obvious answer, which you may have guessed, is to reduce greenhouse gas emissions. While solar energy systems are not emission-free, they contribute significantly less carbon dioxide (CO2) to the atmosphere than natural gas-fueled methods. Even when considering emissions due to manufacturing, shipping and construction, solar energy systems emit 10-20 times less carbon dioxide than natural gas methods. This “apples-to-apples” comparison is easy to make, resulting in little to no argument over which technology is superior regarding CO2 emissions.
In the case of efficiency, however, there is more to consider.
Efficiency is the comparison between inputs and outputs. It measures how much output you can expect for a given input. In the electricity generation world, efficiency commonly refers to the amount of electricity produced for each fuel unit. Natural gas plants can convert 100 units of fuel into 40-80 units of electricity. By comparison, solar energy systems convert 100 units of fuel into 20 units of electricity.
The key difference between Solar Energy and Gas Turbines? The fuel.
While our industrialized world uses fuels like gasoline, natural gas and coal the original and most abundant fuel on earth is sunlight. Every 45 minutes, enough solar energy reaches the Earth to power humanity for an entire year. Plants have been taking advantage of this energy source for billions of years, utilizing the highly inefficient process of photosynthesis to convert sunlight into useful energy. Most plants on Earth boast efficiencies of less than 1%, with the most efficient crop plants today topping out at 2%. And it’s important to remember that this inefficient conversion is simply the first step in producing fuels like natural gas.
Millions of years ago, plants and animals feeding off the Sun’s energy died; they became trapped in geological formations, producing coal, oil, and natural gas.
Today, we invest in surveying, drilling, producing, refining, shipping, and finally burning these fuels to convert ancient solar energy into electricity. Natural gas turbines operate similarly to an aircraft engine; converting chemical energy into rotational energy by burning natural gas to produce very hot, high-pressure gasses that spin the turbine. When a turbine is connected to a generator, the rotational energy is converted to electricity. In a nutshell: energy from sunlight hitting the earth millions of years ago is converted into electricity through a long series of steps.
Solar energy, on the other hand, converts sunlight directly into electricity. Inside a solar panel; energy from the sun excites electrons within the silicon, allowing them to move freely and do useful work. There is no chemical reaction, no moving parts or substances, and no emissions. However, the key factor is that sunlight is free, infinite, and available anywhere on Earth.
This means that when comparing a 40% efficient gas turbine to a 20% efficient solar energy system, we conclude two things:
- An accurate comparison of efficiency (apples-to-apples) would consider the full lifecycle of the fuel (sunlight) for both natural gas and solar energy generation.
- The fuel costs for gas turbines are infinitely more than solar, regardless of efficiency
But the conversation doesn’t stop there.
Technological advancements in solar and the benefits of distributed generation are also important factors to consider.
When electricity is passes through a wire, some of energy is lost due to heat. In fact, around 6-8% of all electricity generated is lost this way. Distributed generation tries to solve this and refers to installing many smaller generators close to where energy is needed. This improves efficiency, reliability and reduces the need for power lines and other energy transmission infrastructure. While utility-scale solar, nuclear and fossil fuel-based generation do not realize these benefits, residential and commercial solar energy systems certainly do. With around half of all solar energy generation falling into this category, solar is at the forefront of distributed generation and reducing transmission losses.
This is great news because transmission systems are costly. Two recently completed 350km High Voltage DC lines (Atco and AltaLink) run from Calgary to Edmonton; and cost a combined $3.5 billion to build.
The final factor to consider is the progression of technology.
There have been numerous advancements in natural gas turbines since John Barber first filed his patent in 1791. For example, “combined-cycle” gas turbines use waste heat from the gas turbine to run a secondary steam turbine. Conversely, the physical principle that allows solar cells to generate electricity (photoelectric effect); was not proven until Einstein published his Nobel Prize-winning article in 1905. This means solar technology has had less time to refine and improve, or in other words, has much more improving to do. In fact, while current commercially available solar panels are around 20% efficient, solar technologies are being tested today at nearly 40% efficiency. And with a theoretical efficiency limit of 70%, the future looks bright for solar energy science.
So which is more efficient? Solar Energy or Gas Turbines?
There is no debating it; solar electric generating systems are less efficient than gas turbines. They convert less of the incoming fuel into electricity. Despite this, solar systems are installed in record numbers both globally and in Alberta. Some benefits to solar are obvious, like the impact of global warming, while others may be more complicated, reducing transmission line losses and costs. What ISN’T complicated, is a solar panels conversion of sunlight directly to useful energy. Plants do this through photosynthesis at efficiencies below 1%, while gas turbines burn these dead and decayed plants as fuel.
20% efficiency starts to sound pretty good when converting a free, available fuel available anywhere and in infinite supply.
In the case of solar energy, the sky’s the limit, literally.
For more information on what solar can do for your business, reach out! We’re happy too help.