Solar powered worksite

There is something fascinating about construction sites.  People walking along the footpath stop and watch what our builders are doing.  Perhaps the sound of power tools catches their attention and causes them to pause to see what is happening.  I can imagine a look of confusion on the faces of the more knowledgeable pedestrians.  They’re the ones who can see power tools plugged into wall sockets on the shed, but can’t see any overhead power lines connected to the service pole on the footpath.  Where is the electricity coming from?  The answer is the sun.  This worksite is solar powered!

Experimenting with a solar powered worksite.

Our builder, David, looks for every opportunity to practise what he preaches when it comes to sustainability.

While putting together the construction schedule, David saw there would be a gap between the date he started and when grid electricity was probably available.  Builders rely on their power tools.  Some are battery powered and can be charged at home.  However, tools such as circular saws need mains supply 240V power to work.  They must be plugged into a GPO on site.

The missing electricity connection gave David the chance to try an idea he’s mulled over for a while.  Is it possible to run a solar powered building site?  How far into the construction process could he go without any connection to the grid?  We were happy to support him with this experiment, knowing that we’d supply him with Powershop Greenpower from a wind farm if he needed a grid connection at a later date.

Solar powered means an off-grid system.

David and his electrician put their heads together to come up with an off-grid solar powered system.

Four solar panels are sitting on the carport roof, producing up to 1.2 kWhr of electricity in the middle of a sunny day.  The carport roof is an ideal location as it faces north.  Luckily for us, the roof stays in place until construction on the second home starts later this year.  I’ll explain what happens to the solar panels after the carport is dismantled later in this post.

The solar panels feed an off-grid inverter which is connected to two Narada AGM-Gel batteries.  If my calculations are correct, the batteries are capable of storing 4.8 kWhr.  Electricity for the power tools comes from a combination of the output from the panels and batteries.  The batteries are essential to provide a reliable electrical supply on cloudy days.

How goes the experiment?

On site, it’s so far so good with the power supply.  David commented it’s a different way of thinking when tools are powered by the sun. Energy conservation becomes essential when you rely on solar panels and batteries.  David and his crew have to consider how power is being used on the site to ensure they aren’t wasting electricity.  This is a similar feeling to the range anxiety we occasionally experience when driving the Nissan LEAF.  Will we have enough in the batteries to get home?  For David, it’s a case of will he have enough power to get the job done that day?

The experiment is underway.  What is the limit on a solar powered site?  Will we have to get a grid connection for the build?  Time will tell.

Future for the off-grid system.

Before starting on the second home, the carport must be dismantled because it’s sitting where the new home is going.  So, what’s happening with the solar powered off-grid system?  It’s going to be reused, like so many other things on this project.

The panels and batteries will move to the recently constructed garden shed, located at the rear of the property. More about the shed in the next post.  David showed us what he could do by reusing materials from the dismantled house as cladding on the shed.

Rather than spend money on running electrical cables all the way to the back fence, we’ll reuse the off-grid system to power the shed.  That means we have a solar powered pump to supply the watering system from the rainwater tank at the back of the shed.  The sun will also power the lights and any electrical tools that I use in the shed.

Who knows what other electrical devices I’ll hook up to the system to take advantage of solar energy.  Mmm, perhaps I could set up a pump to occasionally put a flow of water through the “dry river bed” planned for our garden …

 

• batterieselectricityreusingsolar cellssustainable design