Wind Vs Solar — Which is more Efficient?

This year’s pandemic has renewed investors’ interest in Renewables, as it’s a clean energy source that generates a stable income. Many experts have made various claims regarding the efficiency and viability of Renewable Energy sources, such as Wind & Solar.

As an expert in this field in India — I thought it would be best to lay down the facts about which of these two energy sources is more efficient, their benefits & drawbacks, and investment returns.

Efficiency based on Plant Load Factor (PLF):

Wind Energy is much more efficient than Solar Energy in this case. Most windmills that were built in India between 2005–2015 average a PLF of 15–20%. Some windmills at sites with very high winds have an average PLF of up to 30%, and the new 2.7MW and 3MW wind turbines can achieve a PLF as high as 55–60%! However, the biggest drawback is that Windmills can only work in locations with sufficient wind speeds.

Mono-Crystalline Solar Panels can achieve an efficiency of 21%. The PLF of Solar modules is highly dependent on various factors such as, the quality of modules and the way they are installed, the solar irradiation levels at the plant, and how regularly the panels are maintained. One can install Solar panels in any place with clear sunlight, which is the pre-dominating advantage it has against Wind Power.

Benefits -

1. The energy produced is clean, the parts are re-cyclable!

Solar and Wind are both non-polluting, renewable sources that emit zero carbon emissions.

We can recycle 85% of Windmill’s parts, and there is research going on to increase it 100%. Materials used to make solar panels can be recycled, too, if each layer’s components are taken apart.

2. They are easy to maintain

It is relatively easy and cost-effective to maintain Solar Plants. The only requirement is to keep cleaning the panel, which can be done with clean water and a mop. With an engineer visiting once in a quarter, breakdowns at Solar Plants become extremely rare. Most plants operate 99% of the time.

Wind Turbines require more skilled maintenance as it involves many spares, oil changes. We may also occasionally need to use a crane, as the turbines are situated at a height of over 70–80 meters. However, there are lower chances of breakdowns if the servicing is done correctly. Our windmills have been operating for 98% of the time for the last 5 years.

3. The running costs of the plant is low

Since there is no raw material, the only running cost for these plants is what we charge for regular maintenance. Between the two, Solar is extremely cheap to maintain with an average maintenance cost of Rs 450 per KW, while Wind costs 2–3 times more at Rs 1,000–1,500 per KW. Windmills require 24/7 supervision, and also requires more technical man-power which increases the labour costs.

The cost of spares for Solar is negligible as the panels are covered under a 25 year performance warranty, while the inverters come with extended warranties of up to 10 years. The structure also comes with a 10 year warranty, which means you may not need to spend out of pocket on replacing parts in the PV plant.

4. It’s Cheap Energy!

New Wind & Solar plants are providing power at a cost that’s much cheaper than Coal and Gas (Thermal). Hence, there has been minimal construction of new Thermal power plants as renewables are cheaper and environmentally friendly.

Drawbacks -

1. Both have low-capacity utilization (when compared to Thermal Power Plants)

Thermal Power Plants can have PLF’s as high as 95% subject to regular maintenance.

2. Location

Renewable energy is very location dependent.
Windmills work best in areas with high wind speeds. In locations with less than sufficient Wind, windmills are unviable.
On the other hand, we can theoretically install a Solar Plant anywhere, but the eventual output is dependent on the solar irradiation and temperature levels. Hence, a solar plant in Rajasthan would generate much more than a solar plant in Shimla.

3. Intermittent Nature of Power

Solar and Wind are extremely nature dependent. Solar only works when there is sunshine, while Windmills are heavily dependent on wind speed to operate. Hence, during monsoons, windmills generate more power due to high winds and rains, while Solar generates considerably less power due to the clouds’ blockage of sunlight. Moreover, Wind generates more power during evening and night when the earth cools down while Solar generates power only during the day.

As depicted in the graph above, during the day Wind Power generation drops, while solar picks up. During the night, Solar generation is zero, while Wind peaks at night.

This is actual data from our windmill farm in Rajasthan in August 2020

This is actual data from our windmill farm in Rajasthan in December 2019This is actual data from our windmill farm in Rajasthan in December 2019

This is actual data from our windmill farm in Rajasthan in December 2019

In August since it was the monsoon season, the wind speed was much higher and we were able to generate more power during the day as well. However December was winter and a cooler/ dryer month in Rajasthan which is a desert, therefore the generation dipped drastically and it was more pronounced during the day.

Solar generation works only 6am — 6pm in a bell curve fashion with peak generation around 12 noon to 1pm.

The demand for Power increases when Solar generation drops, making it a key drawback.