How Grid Connect Solar Power Works

While solar technology can be very complicated, the principles of solar power generation and use are fairly simple.

In Tasmania, this is how we setup solar panels and connect them to the power grid:

  1. We install your solar panels and an inverter.
  2. We submit the paperwork to Aurora.  They install a smart meter (to measure power going to and from the grid).
  3. The solar panels will then be in use, fully connected to your property and the grid.

Every millisecond, generated power either travels from the solar panels to the property (for immediate use) or to the grid to be distributed elsewhere.

When the property is using power, the solar system will provide it. If the property is using more power than the solar system is generating, additional power is taken from the grid.

Whenever the solar panels produce more power than the property is using, this excess power is fed into the grid and a credit is given on the property’s power bill.

How Solar Works

The Inverter

Inverters are devices that are installed between the solar panels and the supply board, or sub board. There are 2 types of inverters, string inverters and micro inverters. String inverters are installed the area of the mains or sub board, whilst micro inverters are installed on the back of the solar panels.

The purpose of an inverter is to convert DC power (produced by the solar panels) to AC power. AC power can then be used at the property or fed into the grid.

Connecting to Power Tariffs

For domestic systems, the inverter is usually connected to the Tariff 31 (lights and power).  For commercial systems, the inverter is usually connected to peak rate tariff.

You can move hot water and other demand systems, like pumps, across to the main tariff so they can be powered by the solar system, but this should be evaluated carefully. We can assist by evaluating your circumstances and recommending the best option.

Feed In Ratios

The feed in ratio is the relationship between how much power is used from the solar panels directly and how much power is fed into the grid. The ratio for each premises is different.

The main factor is time(s) of the day that you use power, the size of the system you install and the amount of power that you use. Typically, we see domestic solar installations feed more power into the grid and commercial solar installations use more day time power and feed very little of it into the grid.

Typical Feed In Ratios For Households

Do you use your power mostly at night time? Or do you stay home during the day and use plenty of power then? Remembering that your domestic solar system is connected to tariff 31 (lights and power).

To explain what we mean here, we can talk about a typical day in the life of a solar grid system owner. They wake up in the morning and the sun is up and the solar system is producing a little bit of power. The house will use the solar power while the family has the TV on, the computers are fired up, the kitchen appliances are being used, and the bathroom appliances are being used, and so on. At this time, a family will typically use the power from the solar system and not feed much power into the grid.

Each KwH (kilowatt hour) they use from the solar system has a value of the current retail price, because the household does not need to purchase the power from the grid to power their home. But we digress.

The family then goes off to their various activities for the day. The children go to school and parents to work, etc. All the appliances are off or in standby and very little power is used in the house. The sun is getting higher in the sky and the solar system is just starting to hit its straps and is producing much more power. Obviously the house is not demanding that power and power cannot stand still, so it is fed into the grid. The current travels to the power lines and is drawn into a neighbour’s house as they demand the power.

Also the feed in ratio will depend on the size of the system you have installed and the amount of power you consume. For instance, if you are a big consumer of power even when you are not at home and you have a small solar system (6 panels or so), you will find that your solar system will not feed much power into the grid. The opposite is also true. If you consume a small amount of power but have a large solar system (40 panels maybe), you will find that you feed an enormous amount of power into the grid.

It can be difficult to predict power usage so we draw on our experience of systems already installed. The solar industry generally quotes 50% used off the roof and 50% fed into the grid (50:50). Our research indicates that:

  • a household where families are out during the day are more likely to be 30%-40% used off the roof and 60%-70% fed into the grid.
  • a person who is at home during the day, will generally feed in a lot less power because they consume a lot of it during the day.

A Jessups Solar Squad case study has revealed that a 9am-5pm, 5 day a week, small business in Invermay (Launceston) fed in a 12.8% of the solar power produced into the grid. This is a typical example of a daytime usage of power at home.

If you have any questions about solar power, how it works or your expected feed in ratio, please contact us, we are happy to help.  For a free analysis of how solar will work at your home or commercial property, request a free analysis from us today.

 

You may still have some questions about using renewable, green energy. If you still have any pressing questions that we haven’t answered, please do not hesitate to contact us on 1300 552 785 or 6331 6933 immediately.

John Thirgood
Managing Director,  Jessups Solar Squad

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