Efficiency Of Solar Energy: Compared with alternatives
Efficiency is a parameter that tells about the performance of any energy source or instrument. We can compare the performances of several solar cells by comparing their efficiency.
This parameter is defined by the output energy (electrical energy) ratio and input energy received from the sun. Usually, solar panels are 15-22% efficient.
The efficiency of a solar cell depends on many factors. Here we’ll discuss them, and we’ll also compare the efficiencies of other alternative energy sources.
Dependence of Efficiency on Different Factors
Determining factors
· Types of panel
· Placement, orientation, inclination, and wiring combination of the panels
· Temperature and incidence of radiation time and overall weather conditions
Types of Solar Panels
We can find different types of solar panels. The most popular ones are Monocrystalline panels, Polycrystalline panels, and Thin-film panels.
It’s necessary to specify that the overall efficiency of a solar panel isn’t the same as the individual solar cells of the panel.
While the efficiency of solar cells can reach up to 42% in some cases, solar panels are only 15-22% efficient. So, the efficiency of the cells doesn’t reflect the efficiency of a panel.
Also, we have to keep in mind that efficiencies of solar cells are measured in laboratories under standard conditions where the real-life scenario is quite different.
Monocrystalline solar panels
This is the most efficient type of panel among the three types mentioned above. These are single-crystalline cells made of pure silicon. These panels are dark in color and have rounded edges, and they can show 22-27% efficiency under standard conditions.
Polycrystalline solar panels
They are slightly less efficient than the monocrystalline ones because of the silicon crystals, and silicon is grown as a block crystal rather than single cells, and they are 15-22% efficient. The edges are square in shape and blue in color.
Thin-Film solar panels
They are usually flexible and low in weight. These are made by covering a glass substrate, plastic, or metal with thin layers of PV materials.
The production procedure is less complex than the others, and they are also 15-22% efficient. With the improving technology, thin-film panels are installed to even large-scale projects.
Weather Condition Dependence
There is a huge effect of weather conditions on the output of solar panels. In colder countries, snow and frosts are problematic as solar panels stop working with a layer of snow thicker than 5 cm.
Solar panels are so oriented (tilted) that the snow can slide off in these situations.
In windy weather, it is seen that the efficiency of solar panels decreases very slightly with the increase in wind velocity. Besides that, wind flow also cools down the solar panels as a slight decrease in Temperature helps increase efficiency.
The efficiency of solar panels is also affected by the chemical residue of rainfall, and it is seen that it can reduce efficiency up to 0.2%. There are hybrid solar panels that can generate electricity from the force of falling rain on the panel’s surface.
These are called all-weather solar panels. This new kind of panel has in-built nano-generators. Though they are not as much efficient as solar cells, they can supplement power on a rainy day.
UV rays of incident sunlight also reduce the efficiency of solar panels. Exposure to sunlight builds a layer of boron-oxide on it, and that reduces efficiency by 1-3%.
Highly humid weather can cause corrosion and module connection failure, leading to an overall decrement in solar panel efficiency. Electricity production can drop by 10-25% in partly cloudy weather.
The efficiency drop on a cloudy day depends on how frequently the clouds pass, and also, sometimes sunlight peeping from the edges of clouds intensifies the incident irradiation. That surprisingly raises the efficiency.
Temperature dependence on the efficiency of solar panels can’t be denied. Solar panels show maximum efficiency between 59 and 95 degrees Fahrenheit, and efficiency drops by a temperature coefficient of 0.5% degree Centigrade.
Efficiency also depends on the incidence irradiation. In tropical countries, incidents and radiation are greater than in colder countries.
Comparing Efficiency with Alternative Energy Sources
· Nuclear Energy
· Wind energy
· Hydroelectricity
· Geothermal Energy
· Biomass Energy
· Tidal and Wave Energy
· Non-renewable Energies
Comparing Solar Power Efficiency With Nuclear Energy
The energy consumption of the whole world mostly depends on fossil fuels that are very harmful to the environment. But none of the alternative sources could replace it entirely.
The strongest most competitor of fossil fuel is nuclear energy that can provide as much energy as fossil fuels. Also, this can be considered as the largest carbon-free electricity source in the world.
Typical nuclear power plants show efficiencies around 33-37%, and Fourth-generation reactors can potentially reach even above 45% efficiency. Nuclear power plants can operate 24/7 at a 93% average capacity factor (Capacity factor is defined by the ratio of the actual amount of electricity generated and the maximum amount of electricity it can potentially generate).
That’s more than the capacity factor of any other carbon-free electricity source. Technically it’s much more efficient than solar energy. But the main problem with it is the nuclear wastes.
Comparing Solar Power Efficiency With Wind Energy
Wind efficiency is the amount of kinetic energy of the wind that converts into electrical energy. If the wind stopped blowing, the blades would stop and couldn’t produce electricity. The maximum theoretical efficiency limit is 59.6%, and the average efficiency the turbines show is 35-45%.
Energy efficiency doesn’t vary as much as the wind capacity factor, and the capacity factor varies according to location and weather conditions. It can be optimized by choosing places where ideal wind conditions prevail most of the year.
Increment of capacity factor is being noticed with the advancement of technology. Wind turbines manufactured in 2014 reached up to 41.2% capacity factor whereas wind turbines of 2004-2015 could reach only 31.2%.
Recent research from Oxford Brookes University has found vertical turbines to be more efficient than the traditional ones.
In large-scale wind farms, these vertical turbines seem to be more appropriate. When set in pairs, they increase each other’s efficiency by 15%. This is more efficient than solar panels as they are only 15-22% efficient. But, wind energy isn’t available everywhere as solar energy is.
Comparing Solar Power Efficiency With Hydroelectricity
Hydroelectricity is one of the huge sources of green energy. This is much more efficient than any other renewable energy source. Nowadays, a hydroelectric plant is almost 90% efficient.
Over the years, this has been the world’s most affordable electricity. If we check the capacity factor of hydropower, we can see that it varies from plant to plant much more than any other energy source like wind or nuclear energy.
Most plants have capacity factors within a range of 25% to 80%, while solar energy is 15-22% efficient. The weighted capacity factor for small and large hydropower projects is around 50%, while the mean capacity factor of solar panels is 29% (ranging from 18%-33%).
The high range of capacity factor is quite expected due to the flexibility of design of the plants, different amounts of inflows, and different site characteristics. Also, low capacity is a design choice to meet peak demands, and it doesn’t affect the project economy.
Comparing Solar Power Efficiency With Geothermal Energy
Geothermal energy is considered to be one of the most efficient and environment-friendly energy sources. Tectonic plate boundaries where the crust of the earth is thinner have the highest Temperature underground.
It can produce electricity with a possibility of 300-400% efficiency and almost zero emissions. The ability to have 400% efficiency comes from the fact that energy is being harnessed here.
Efficiency depends on factors like mass flow, cooling methods, geo-fluid Temperature, etc. Increasing mass flow also increases efficiency as the work rate increases higher than the heat flow due to increasing mass flow. The Temperature of cooling water needs to be lowered to increase the efficiency of the plant.
This is the only power plant that can compete for the capacity factor of nuclear power plants. According to 2019’s report, the capacity factor is over 90%. It looks like its efficiency is enormous compared to solar energy. But, again, if one looks at the energy cost, then solar energy looks more feasible.
Comparing Solar Power Efficiency With Biomass Energy
The efficiency of biomass energy into power, heat, transport fuels and chemicals mostly depends on the various methods (both thermochemical and biochemical) used for its conversion.
The overall efficiency of biomass-based power plants varies from 70% to 90%, whereas solar panels are only 15-22% efficient. This is relatively high and very environment-friendly as it absorbs more carbon dioxide from the atmosphere than it releases.
But still, this isn’t as much available as solar energy. Dry biomass feedstocks have high heating values, and wet waste biomass has lower. Efficiency depends on the energy contents of the feedstocks. So, using dry feedstocks results in higher efficiency, and using wet ones results in lower efficiency.
If we check for the capacity factor of biomasses, we can see that woods have a capacity factor of nearly 58.4%, whereas other biomasses have around 63.2%.
Comparing Solar Power Efficiency With Tidal and wave Energy
Tidal turbines are around 80% efficient. A tidal range varies from site to site over a wide range. It may vary from 4.5 m to 12.4 m. we need at least 7 m high tides to make the turbines work.
But although nowadays technology is advanced enough to harness tidal energy, it is costly. Also, it doesn’t have enough potential to supply accordingly with the huge energy demand. Capacity factors of tidal turbines are low too. It is usually within a range from 20% to 35%.
On the other hand, the efficiencies of hydraulic turbines (powered up by waves) can reach from 70% to 90%. There are power take-off systems that can convert wave kinetic energy to electricity. There are currently 42% use of hydraulic systems, 30% direct drive, 11% hydraulic turbines, and 11% pneumatic systems.
Both are more efficient than solar energy, but they aren’t available everywhere like solar energy does.
Comparing Solar Power Efficiency With Non-Renewable Energy (Fossil Fuels)
These are the most popular energy source all over the world. Despite it being so harmful to the environment, no other energy source can replace it entirely until now.
Fossil fuels are the most energy-dense source of all other available sources. For example, natural gas provides 53.1MJ/kg, gasoline provides 45.8Mj/kg, coal provides 30.2 MJ/kg, and wood provides 19.8 MJ/kg, and lithium-ion batteries provide 0.504MJ/kg.
Gasoline that is used in cars as fuel is somewhat 20% efficient. That means 20% of them convert into mechanical energy of engines, and the rest 80% is wasted as heat energy. Coal is 33-40% efficient while producing thermal electricity.
But they provide energy to the world and suffocate the earth. Also, they contribute significantly to global warming.
In the case of thermal electricity, there is considerable energy loss in different steps. Due to incomplete combustion and exhausted heat, the entire energy attained from burning coal isn’t transferred to steam produced by the boiler. Still, modern boilers can achieve 90-94% efficiency, and that’s a significant amount.
Energy loss from the energy sink used in the power plant caused by the efficiency threshold is 64-67.5%. The thermal efficiency of a modern thermal power plant is usually 35-49%, and current generator efficiencies are pretty high (96-99%).
Thermal efficiency depends on a few factors. One of them is the temperature difference between the hot and cold reservoir, and other factors are initial pressure and exhaust pressure. By increasing initial steam parameters, efficiency can be enhanced.
Conclusion
As we can see, almost every other alternative source is more efficient than solar energy. But we can’t still deny the environment–friendliness of solar energy. And also this is much more available in almost every geographical region and different countries.
Though nuclear power is the best option to replace fossil fuel, it isn’t that popular. The reason is that the pollution from nuclear wastes is huge, and solar energy is at least harmless.
