Do Solar Panels Work At Night?
Solar panels have been popular in the past ten years and it doesn't seem to be slowing down anytime soon in Australia. As reported by Energy.gov.au, "Australia has the highest uptake of solar globally, with more than 21% of homes with rooftop solar PV. As at 31 May 2020 more than 2.43 million rooftop solar power systems have been installed."
Although Solar PV systems aren't new, many people are still confused on how exactly the technology works (even those with solar installed), but more importantly, they do not know how exactly it reduces the typical electricity bill. So how do solar panels produce electricity? Do solar panels work in cloudy weather? What about at night?
What are solar panels?
Essentially solar panels are made up of several smaller units known as solar cells. These devices work by gathering light provided by our ever shining star - the sun. They then convert the light into direct current (DC). A single panel will just generate electricity enough for 1 or 2 small appliances. To create a solar system that can power a house or building, you would require an array with many panels connected together – just like an electrical circuit arranged in your home.
How do solar panels work?
As the solar panels convert light into power (DC), the power gets sent through the system's inverter. From there, it gets converted to alternating current (AC) power. AC is the power most households run on. This is what you get when your utility grid feeds electricity into your home for you to use to watch television, turn on the lights, and so on.
Any power produced by your system that you don’t use gets sent into battery storage or the grid. Solar systems work best when most light hits the cells. How well the cells converts it to DC power can produce the most electricity for the household. So then what happens on a cloudy day?
Do solar panels work in cloudy weather?
Yes, solar panels do work on cloudy days — but not as effectively as they would on a bright sunny day. Expect them to produce 15-25% of their normal power output, depending on how thick the cloud cover is. Although they work better on sunny versus cloudy days, solar panels do not work best in hot climates. In fact, solar panel output begins to decline if the temperature rises above 25 degrees Celsius. You can relate this back to a normal electrical circuit when it gets too hot – more resistance in the circuit.
Because of this, solar panels work better in certain areas than others. The areas with cooler weather keeps the device at an optimum temperature for energy output than for those areas in sunnier and hotter days.
In summary: on cloudy days solar panels do work; just less effectively. And solar panel performance also drops when it is too hot. That being said, solar panels can work and is worth the investment across a range of different climates.
Do solar panels work at night?
The answer is no, they don’t. As seen in the graph below for a typical household solar export and grid use. The yellow bars are grid use, and the green bars are the solar export. It clearly depicts that solar panels do not generate electricity at night time. This is actual data (energy retailer) from a household with a solar PV system.
Figure 1. Typical Day and Night Use of Solar and Utility Grid
As we mentioned earlier, solar panels need light, preferably sunlight, to create energy. Although they can generate some energy from other light sources such as street lights, the output is very low. Because of this, we should not rely on solar panels to power our Netflix binge night.
Then how do homes with solar panels have power at night?
Solar panels produce no electricity at night, but they tend to produce extra power during the day when the sun is out. In order to balance things out, and keep the electricity running after dark, solar customers use either solar battery to store energy or net metering.
Solar battery storage
The concept behind solar energy storage is simple. Solar systems should be intentionally designed to produce more power than your home needs during the daytime. The surplus power generated during the day is stored in a solar battery solution such as the Tesla Powerwall 2.
At night, when your solar panels are not generating, you can use the stored energy held by the battery system to power your home. Some houses with his setup are even able to operate off grid, i.e completely independent of the utility.
Net metering - like using the grid for storage
If your solar panel system doesn't have storage, you can still use your surplus solar energy at night - through net metering! With net metering, you don’t have physical energy storage at your home.
Instead, the excess power your solar panels produce during the day is exported to the utility grid. You receive credits (feed-in tariff) for this power, which accumulate in your energy account.
Later, at night — or any other time you use power from the grid (see Fig 1) — you can use your credits to offset the cost of the energy. In other words, net metering lets you store the economic value of the excess power you produce, which you can use to reduce or even completely cancel out your electric bills. If the solar PV system is planned out properly, net metering makes solar power even more economic sense. For more information on net metering, go to https://www.finder.com.au/what-is-net-metering.
Net metering is the answer to those questions, who think solar is not for them because they are not home most of the time during the day time. The question you should try to quantify first is 'how big of a solar PV system I can put up on my roof?' Then, the next question is whether it makes economic sense for you (the 'pay back period') if you do decide to install solar.
In summary, solar PV systems do work on cloudy days and actually works better when it’s not too hot. How efficient your panels are under different weather conditions will depend on your solar panel brand; so be sure to check out the manufacturer's module datasheet before deciding on the panel.