What is a megawatt hour (MWh), and what is its relevance to solar power?
A MWh refers to 1000 units of electricity, where one unit of electricity is 1 kWh.
The term Mega usually refers to a million; you might hence wonder why it is just 1000 units of electricity, and not a million. This is because, the lowest unit of electrical energy is not kWh but Wh, though kWh is the unit used for one unit.
Megawatt Hour – A MWh is a million watt hours, or 1000 kWh.
Thus, a MWh is a million watt hours, or 1000 kWh.
Questions from the curious cat
How many MWh of electricity does a 1 MW solar power plant generate in a day? In a year?
Depending on the region and its DNI ( a measure of amount of sunlight available), a 1 MW solar power plant can generate between 3-4.5 MWh of electricity a day, or 1100-1600 MWh of electricity a year. This equates to 1.1-1.6 million units of electricity a year, per MW (recall that 1 MWh equals 1000 kWh, and a kWh is the unit of electricity).
Why does a 1 MW solar power plant not generate 24 MWh of electricity a day? This is because 1 MW is the rated capacity that is applicable only for good sunshine hours. However, sun is available only between 7 AM and 7 PM, and even during this period, peak sunshine is available only for 2-3 hours. As a result, what a 1 MW if solar panels can produce during a day is much less than 24 MWh.
For comparison, how many MWh of electricity does a conventional thermal power plant generate every day? Every year?
A conventional thermal power plant (using coal or natural gas) has a capacity utilization factor (CUF) of about 80%. This means that the plant is able to produce a total output that is 80% of its maximum capacity.
With this CUF, a conventional power plant produces about 20 MWh of electricity every day and about 7000 MWh (7 million units) of electricity every year.
Solar power plants have CUFs of only about 17-20%, or sometimes less than that, resulting in only about 1.5 million units per MW on average.
7 million units for a conventional thermal power plant vs just 1.5 million units for a solar PV power plant.
This quick comparison of solar and conventional power plants shows that a solar power plant generates only a bit more than 20% of the total generation of a conventional power plant.
This low CUF of solar power plants is one of the drawbacks of solar power.
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