Friday (April 22nd) was Earth Day and it also marked the completion of our second year living in, and monitoring the performance of, the Greeny Flat. So we marked both occasions with a little party.
Thanks to everyone who came along to help us celebrate two wonderful years in our lovely little house.
Second Year Results
The results of two years of monitoring the energy performance, water usage and comfort levels in the Greeny Flat can be viewed on our Results Page here. The second year’s results prove that the first year wasn’t a fluke. In total we have exported almost three times as much power to the grid as we have imported from it. Not surprisingly, those figures have changed quite a bit since we bought our Plug-in Hybrid Electric Vehicle (PHEV) in December and started charging the batteries using some of our excess solar power during the day. Prior to the PHEV our average export per month was 302kWh and our average import was 102kWh over 20 months. In the four months post PHEV our average export was 280kWh and our average import was 150kWh. It’s still early days and those numbers come from four warm and sunny months. It will be interesting to see how they change again during the colder and darker winter months.
The great news is that, despite the fact that we are now doing quite a lot of our driving using our own renewable energy, we are still exporting a lot more power than we are importing.
Import/Export Versus Production/Usage
It is important to understand though, that the amount of energy we import and export is very different from the amount of energy we actually use and produce. To understand this you need to understand how ‘net metering’ works. During the day, the energy that we make from our solar power system goes to the house first and then any excess is exported to the grid. If we are not producing as much power as the house requires (e.g. periods of high energy use like cooking pizza for thirty guests; or when the weather is cloudy; or at night) we import power from the grid to make up the shortfall. So our export meter does not ‘see’ the energy that went straight from our solar system to the house, thus our actual production is higher than the amount we export. Similarly, our import meter does not ‘see’ the energy that the house has used directly from the solar system, thus our actual usage is higher than the amount we import.
I understood this principle from the beginning but it took me quite a while to figure out how to obtain our actual production and usage numbers. Thus we only have those Results for the last six months. For anyone with a solar system on net metering, the way to obtain your total production figure is to look at your inverter. Our SMA inverter has a digital display panel that shows the total amount of energy generated. There is a way to connect a computer to the inverter using bluetooth but I haven’t figured that one out yet. So on the 22nd of each month I simply read and write down the total energy produced by the inverter along with the meter readings for import and export, town water and tank water used. I put those numbers into a spreadsheet which then tells me how much energy we have produced, used, imported and exported each month.
In order to calculate the total amount of energy you have used you need to take the total production figure for the month (from the inverter reading), subtract the amount that was exported to the grid (this tells you how much of your own power you used in the house) then add the amount that was imported from the grid. This gives you how much power you used in the house for the month.
Usage = (Production – Export) + Import
The following is an excerpt from our Results Page which shows (circled in red) the difference between our average daily import/export readings and our actual usage/production.
You can see that, for the last six months, on average we exported 10.0kWh/day and imported 3.6kWh/day. So we exported almost three times as much as we imported. During the same period we produced 13.2kWh/day and used 7.6kWh/day. In other words, we made almost twice as much power as we used.
Please note that the amount we used is more than twice as much as the amount we imported from the grid. If we’re serious about reducing our carbon footprint and the amount of energy we use it is very important to understand how much power we are actually using. In the near future, ‘Smart Meters’ should be able to ‘talk’ to inverters and in-home energy monitoring systems as well as to the National Energy Grid. We should all have a prominent display in our homes that shows us, in real time, how much energy we are producing, using, importing, exporting and storing in our batteries (and vehicles) plus the current price of energy at any given moment. These Smart Meters should communicate with our Energy Management System to decide when to import and export, when to store energy in home or car batteries, when to sell power to the grid and, potentially, even when to run the car’s engine as a backup generator for the house or for the grid as a whole.
Imagine if every home, car, business, bus, truck and factory were connected in this way via the grid. It’s coming and it can lead to fantastic improvements in energy efficiency, reduction in carbon emissions, and maximising the return on everyone’s investment in renewable energy systems. Now that will be something to celebrate!
More Good News for Earth Day
The good news is that delegates from more than 170 countries gathered at the United Nations to sign the Paris Agreement on Earth Day. This article from The Guardian describes this as ‘a powerful display of global efforts to fight climate change.’
Then goes on to note that ‘a dozen countries – mainly the small island states at risk of being drowned by rising seas – said they would take the additional step on Friday of ratifying or granting legal approval to the agreement.’
So while 196 countries have symbolically ‘agreed’ to global carbon emissions reductions, only the few that are at most imminent risk of total disaster have actually ratified the agreement so far. Nevertheless, it’s movement in the right direction and should keep the pressure on Turnbull and Shorten to make Emissions Reductions and Renewable Energy Generation important election campaign issues here in Australia.
An Alternative Future For Coal?
We all laughed when Tony Abbott said ‘Coal Is The Future’ and when we heard last week that the largest coal mining company in America, Peabody Coal, had filed for bankruptcy we thought it was further proof (as if any were needed) that Tony was wrong. So wouldn’t it be deliciously ironic if it turns out that he was right, just not in the way he expected.
I’ve just read this Gizmag article about a group of scientists at MIT who have discovered a way to make thin-film electronics which have some of the properties of advanced materials (like silicon and graphene) from unrefined coal at (potentially) much lower cost.
‘According to Professor Grossman, the major advantage of the new material is its low cost to produce from an incredibly cheap base material, allied with an uncomplicated solution procedure that allows exceptionally low fabrication costs. Compared to silicon or graphene for use in electronic semiconductors, coal thin film is far and away the simplest to produce because it doesn’t require such high levels of purification.’
Perhaps our future solar power systems and energy-saving electronics will be made from coal. Perhaps coal really is the future.