We have had our new Tesla battery for a couple of weeks now and we have just done our first electric kiln firing on sunshine.
We have had 3 kW of solar PV panels on our kiln shed roof for over a decade now, but we have only recently managed to get our hands on a new PowerWall 2 lithium battery, after being on the Tesla waiting list for over a year. The battery is working perfectly, just as we imagined, and now allows us to run our house and pottery almost totally independent off the grid. We had decided to stay connected to the grid however, as we generate far more solar electricity than we use ourselves most of the time, and up until recently we got a very handsome rebate payment for the power that we sold.
Now that the generous rebate program has ended, it is much better for us to store our daytime solar electricity excess and use it ourselves at night, instead of paying the premium cost of buying back ‘green’ power from the grid at night.
Of course we don’t have to buy ‘green’ power. We just choose to, because we made a decision 13 years ago to remove ourselves from the coal economy. Which we have done. We are of the belief that global warming is real and that it is man-made. Burning coal to make electricity is a very big part of the problem, and green power is going to be part of the solution. It’s affordable, it’s here now and it’s the future. In addition to going solar, we have also declined to use concrete slabs in our building construction and we choose to drive the smallest fuel-efficient car that we could afford.
When we put the first Australian made solar panels on our roof 11 years ago, we didn’t do it to make money. We did it for ethical reasons. However, as it turns out, we paid off the panels and made a slight profit over the decade, because we were paid one or two thousand dollars a year for the power we sold to the grid, but we also didn’t have an electricity bill for that decade. A saving of many more thousands of dollars. These original PV panels still have another 15 years of full productive life in them, before their output starts to decline. I’ll be long dead before they stop working. We recently added another 3kW of PV at the same time as the battery. As I intend to buy a fully electric car as soon as they become available at an affordable/reasonable price.
So now with everything in place, we have just completed our first electric kiln firing using our own solar power, firing through the day on sunshine up until just after lunchtime and then into the afternoon on a mix of solar and battery, then ending in the evening mostly on the battery power. Yes, it works. You can fire on sunlight. The future has arrived!
Below you can see a graphic of our power usage though the day.
The high blue spikes are the electric kiln switching on and off. The golden-yellow hump in the middle, above the line is the solar panel output from the roof. The green areas below the line is the battery being charged up from the solar PV panels in the morning and corresponds perfectly with the yellow solar area above the line, up until noon. The solar panels are both firing the kiln and charging the battery up to noon.
After 12 noon, there was some cloud that came over and the solar output dropped down. By about 3 pm. the PV panels no longer generated sufficient power to both fire the kiln and charge the battery. After 3pm the clouds cleared and solar output increased again and fired the kiln with the assistance of the battery. From 4 pm onwards, the battery fired the kiln with assistance from the solar. Solar production ceased at about 6.30 and the firing finished at about this time also, more or less solely on battery power.
The small zigzag ripple on the base line is the household usage, mostly this comprises the fridge compressor switching on and off. I should also point out that I was also working in the kiln factory throughout the day and using some very heavy 3 phase sheet metal machinery, welders and plasma cutter. This is included in the blue spikes. The lower line of blue spike peaks is the kiln alone, and the higher level of blue spikes is the kiln and the heavy electrically powered machinery working at the same time.
The following day, the PV panels charged the battery back up to full power again by about 1.30pm. Solar output is shown in yellow. The battery shown in green is being charged below the line. Once the battery is fully charged, the solar output is then switched to sell back into the grid for the rest of the day. Shown in white below the line. Household usage is shown in Blue above the line. You can see that we run a very energy-efficient household. The blue spikes represent the toaster and jug in the morning, then the washing machine and then me using the heavy 3 phase welders, and sheet metal machines intermittently in the kiln factory through the day.
By way of explanation, I downloaded this screen shot at 3.30 pm, so that is why the graph suddenly stops.
From this brief explanation I hope that I have illustrated that it is possible to live a ‘normal’ life, carry on working and fire an electric kiln, all from a solar array and a lithium battery.
Food for thought?
Some technical details;
The battery is a Tesla Powerwall 2 lithium-ion battery with a 15 kWh rating.
The solar array is 6 kW. Made up of 3kW of 11-year-old BP solar panels made in Sydney, and 3kW of new ‘Tindo’ solar panels made in Adelaide. In both cases, we paid a premium to purchase Australian made panels to support Australian industries and Australian jobs. If there had been a comparable Australian battery. I would have bought that instead.
The Tesla Powerwall 2 lithium-ion battery is 15 kW/h rating. Made in the USA. The closest Australian contender was ‘ZPower’ also from Adelaide, but at almost 3 time the cost, it was out of our price range. All these things will change quickly and dramatically over the next few years. Watch this space. You can be sure that whatever will replace our battery at the end of its life in 15 to 20 years time, hasn’t even been thought of yet, never mind being built!
The kiln is one that I made myself. It is a half metre cube 500mm. x 500mm. x 500mm. constructed out of light weight RI bricks.