The unveiling of the Coalition government’s new energy policy appears to lock in Australia’s extraordinary high energy costs for at least another decade. This will encourage yet more households and businesses to turn to solar, and to battery storage to minimise their costs. Some will look to leave the grid altogether to be rid of the high network costs.
This is a story of how one Brisbane family left the grid, the lessons learned, and what others should consider.
In 2014, we decided to move out of an inner city suburb and started looking around for a suitable house on a few acres in a semi-rural area on the outskirts of Brisbane.
Unfortunately, all the housing stock seemed to be 20 years old and had next to zero environmental efficiency.
As we wanted to limit increasing operating costs in our retirement, we began planning to build a new house that had the type of energy efficiency we wanted, and was modern, comfortable and had resale market appeal.
We were always going to have solar, and you need a generator for emergency supply for drinking water pumps, but the house was located 180 metres from the front of block, so we started investigating going entirely off-grid as the cost of the batteries was about the same as the cost of an underground powerline to the road.
To make the whole thing feasible we designed the house to 8.5 star energy rating standard. This included siting the house with a north east aspect well away from overshadowing trees (also helped with BAL fire rating).
We chose fibre cement cladding, light coloured colourbond roof with 65 mm anticon blanket insulation, R4 insulation on the ceiling, R2.7 acoustic insulation in the external walls and R2 i
It was important to upgrade all windows to 6 mm low-e glass. Choosing LED lights throughout, a 315 litre heat pump hot water system, combination gas and induction cooktop and efficient split system airconditioners was also essential.
As summer temperatures in our area can be very hot for long periods we chose airconditioners running on efficient R32 gas, which allows us to have 3 2.5kW units in the main bedrooms, and 7.1 kW and 3.5 kW units in the living and TV areas.
In all the main rooms we have super-efficient DC reversible fans for summer and winter operation to aid air circulation and comfort.
Solar and Batteries:
Our solar system was set up by ECoast Energy, an off-grid specialist from the Sunshine Coast. We have 40 panels set up on the house and garage roofs. 14 panels are on AC coupling maximising northerly and westerly aspect for day aircon and evening loads (7.28kW) and 16 panels on DC coupling utilizing northeast, north, northwest aspects for early battery charge and consistent daily sun path charging (4.16kW).
When we made the decision in late 2014 to use sealed unit lead acid batteries (24 x Bea 2V batteries providing 14.5 Amp hour rating storage) we knew, just like whenever you buy a new camera or computer, they would quickly be superseded by newer, better and cheaper options.
But just like the new camera decision, if you don’t just bite the bullet you end up procrastinating forever.
Knowing this, we opened a bank account and put $50 per month into our “sinking fund” so when we need to replace the batteries they will be bigger in capacity, smaller in footprint, more efficient and cheaper. More on this below!
Our system uses a Midnite DC solar controller which is dedicated to recharging the batteries, ABB (Selectronic Certified) managed AC controller providing direct power during the daytime and additional charging for the batteries and a Selectronic SP Pro inverter for getting the power back out and overall management of the system.
We found it very difficult to get accurate advice as to the combined impact of all the various combination of features you need to get right, so we probably over-engineered it all a bit, just to sure. Then we fine-tuned things over the 12 months we have been living here and we want to share some of this learned experience.
Off-grid Living Experience:
Living in Queensland, energy efficiency is more about keeping cool in summer than winter heating. In the winter just past, even though it was warmer than average, we still had many nights where the temperature dropped in the 2 to 5 degree range.
By closing up the house at dusk, we normally started with an inside temperature of 20 – 21 degrees. Most nights it only went down to 19, with a drop to 18 on the coldest mornings.
We only turned the bedroom aircon heating on 2 or 3 times and then only for 30 minutes. The rest of the time we used no heating at all.
In summer we open the windows at night and close them by 7 am. Inside stays 10 to 15 degrees cooler than outside with no cooling, but if it gets up to 24 we turn on the big airconditioners and turn them off at dusk.
Our batteries usually go down to 80 to 85% overnight with our background usage (3 fridges, appliances on standby etc). On sunny days they are full again by 10 or 11 am. Our heat pump hot water system comes at 11 and stays on till the water heats up to 61 degrees (normally only a couple of hours, but longer in winter). We have enough daytime power to do whatever we want, including pumping irrigation from the creek for the gardens.
To improve the efficiency and comfort of the system we have recently invested in a few external blinds on windows that get direct sunshine and have put in a low-power vented exhaust system in the roof cavity to expel hot air in summer.
The only other thing we would change is (next time?) we would build the house with 900 mm eaves instead of 600 mm to give better shading and weather protection.
Going off-grid requires proper planning and design, but also you have to modify your behaviour in a sensible way, so you put off using dryers and ovens and high use appliances at night and during cloudy weather.
Our main power controller (SP Pro inverter) has been programmed by our installer in consultation with us to protect the batteries by automatically switching on the generator if power is being used to quickly, or if the state of charge of the batteries falls below prescribed levels.
These “business rules” can be tailored to suit our needs and can be modified remotely as required. We hardly ever need the generator on, but when it is required it charges the batteries in an hour or two and doesn’t use much diesel fuel in the process.
We read a lot about renewable energy and many of the stories have come across about other people’s off-grid experience tend to focus on tales of extreme self sufficiency, carbon neutrality and home-made solutions.
Each to their own, but we wanted a modern lifestyle without the hassles of being dragged into the hassles of escalating power prices and anarchic energy policies from big, voracious power companies and inept government leadership and bureaucracies.
The fixation of much of the debate on return on investment and payback periods in our minds had to be balanced against the peace of mind of locking in our energy expenditure up-front. As part of the cost of a new build, the marginal cost of insulation, energy efficient appliances and windows is only an extra few percent.
Our only costs now are topping up the generator every now and then and some LPG for the stove and BBQ. We also have a 130,000 litre rainwater tank so we never run out of beautiful clean, free water. On average, over the past 12 months, we use about 26 kWh of power a day.
On hot sunny days, with the airconditioners going, we sometimes generate/use 35 kWh or more. As we are not connected to the grid, the system only generates whatever power we are using after the batteries have been recharged to 100%.
Replacement Options:
We always looked on our lead acid batteries as an entry point. Since then we have seen all sorts of technology coming on-stream.
Salt water, flow batteries and of course lithium batteries with the big name Tesla making headlines have all advanced the choices now available.
Recently, we have particularly noted the introduction of a turn-key solution in a cabinet the size of a fridge by Melbourne company Arvio. At the top they have an SP Pro inverter, a tiny communications computer, and switching gear (all made in Melbourne).
In the cabinet below, the really exciting bit of kit is a supercapacitor energy storage device –like a battery but using graphene instead lead/acid or lithium.
Unlike traditional chemical-based batteries, supercapacitors can be charged in seconds, are capable of millions of charge/discharge cycles, will not burn or explode and are more environmentally friendly in terms of being made from readily available carbon rather than rarer and more toxic metals like lithium or cobalt. Our guess is that when it comes time to replace our batteries, this will be the dominant technology.
Lessons Learned: Summing up our off-grid experience-
This post was published on October 19, 2017 11:48 am
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View Comments
Great tale. Would you mind revealing the costs breakdown for your power system?
Hi Denby. The system cost about $65K AUD. Breakdown is approximately $20K for batteries, $30K for panels, inverters and switch gear, $10K for design and installation and $5K for the generator. The cost of the underground powerline from the house to the front of the block to connect to the grid was going to be about $20K so the decision to go off-grid was easy. Having made the decision prior to building the house, the subsequent design, material and appliance choice decisions we made were specifically built to work in harmony with the performance of the power system designed by ECoast Energy, our off-grid power experts.
More here on the future of the all-electric home!
https://www.thefifthestate.com.au/columns/spinifex/cutting-the-gas-has-the-all-electric-homes-time-finally-arrived
No intelligent load shifting, no pre-heating, no pre-cooling, no thermal energy banking?
And it looks like minimal insulation, unless AU uses R values that differ from US. I would think that a well insulated enclosure would be essential to living off grid unless you're in a very benign climate.
And how can they operate even just the 7.1kw A/C unit? It would use all the battery storage in less than two hours, even if the system allows that large a power draw. We could use some actual numbers, especially how many hours per year the generator runs and how much fuel it uses.
Cost numbers would be interesting also. That 25,000 gallon water tank wasn't cheap. (The big gasoline trucks you see on the highways hold about 8,000 gallons.)
Smslaw, the R values depend on the units used to calculate them. In Australia, the units are watts, degrees C and square metres. In the US I would expect the units to be BTUs, degrees F and square feet. The resulting R values will not be comparable.
For comparison purposes, 25mm (about one inch) of fiberglass, mineral wool or cellulose insulation has an R value of about 3.5 using US standard.
In my cold climate (Maine) energy codes require R 49 in ceilings and R 20 in walls.
US R-values are based on square feet, Australian on square meteres.
Therefore, just devide the US R-value by ten and you get the Australian equivalent.
Hi smslaw. I think US and Australian insulation ratings are very different. Building codes in Australia now stipulate new housing must be designed to 6 start rating. Our house is rated at 8.5 stars. The external and internal wall insulation is 90 mm thick and the batts on the ceiling are 125 mm thick. Under the metal roof is an anti-condensation foil/fibreglass "blanket" 65 mm thick that insulates and deadens the sound of rainfall. For our sub-tropical climate this level of insulation is considered unusually high, mainly because Australians normally think of insulation as being only for people living down south to keep out the cold. Increasingly, people in Queensland will start using it to keep out the heat. The 6 mm low-e glass we used is just or more important as the insulation. Nobody in Queensland uses double glazing. The glass companies tried to talk me out of it when I inquired, but for our purposes, the coating on the low-e glass works just fine. It greatly reduces noise as well. Most project homes in Queensland just use plain 4 mm glass and I think it is false economy, particularly in a new build situation.
Our climate is relatively benign compared to some parts of the UK. Where we live our summers average around the mid 30's celsius but we are increasingly getting 3-5 periods of week-long heatwaves in the 40's. Winter nights drop to 2 - 5 degrees, but by mid morning our winter temperatures are normally around 20 - 23 degrees. We are also getting an increase in the frequency and severity of thunderstorms. We over-engineered our construction standard to cope with those trends (if you build to minimum code now I think you have rocks in your head!). I was an owner-builder, so it just required a bit more hammering and cyclone tie-downs.
We only use the big airconditioner on sunny days. It is just designed for intermittent use in daylight hours. All our airconditioners are inverter units using the most efficient gas (R32) and the power they draw is much less than their rated output. As our panels can produce over 10 kW on a sunny day and that is when we use them (and we normally only have one or two on at any time) the question of power usage is irrelevant.
We have an 8 kVA Able Sales diesel generator. It has a 1500 RPM water-cooled Yanmar engine that uses about 2 litres of fuel per hour. Our SP Pro turn it on for 15 minutes once a week to keep it happy. The system is programmed to turn it on if the state of charge of the batteries gets down to 60% or if the rate of drawdown of current from simultaneous usage of appliances (oven, dryer, airconditioner) is too high. If it overcast, I sometimes turn it on for an hour or so and it will add about 10% to the state of charge in that period.
It was interesting figuring out how big a drinking water supply we would need. People in our area often have to buy water from local carriers ($125 for 13,000 litres) and we wanted to avoid being in that situation. We capture water from the house, garage and shed, so I calculated the tank size from that area times the local rainfall and added a bit more to be on the safe size. I calculated the cost per litre of various tank types (concrete, polyethylene and lined steel) and found the Rhino tank (steel with a PVA liner) from Western Australia to be the most economical. I was going to get a 90,000 litre one but the 130,000 litre was only a few hundred bucks more, so I thought "what the hell" and bought the bigger one (it was about $9,000). It filled up and has stayed almost full ever since. I the recent dry spell it dropped to about 80% then filled up after 20 mm of rain. Peace of mind and plenty of reserve for fire fighting (it has a 2 inch fire cock for emergency use). Best investment ever.
The kw ratings listed are the rated cooling or heating outputs not the electrical inputs. An average efficient heat-pump unit moves around 3.5 to 4 times more energy than it uses, so less than 2kw even when running flat out for the 7.1kw A/C.
Hi smslaw. Our insulation in the internal and external walls is 90 mm thick (R2 and R2.7). The R4 batts in the ceiling are 125 mm thick and the anti-condensation blanket under the metal roof has 65 mm of glass fibre and foil reflective surface on the bottom. This is considered a lot of insulation for our sub-tropical climate. It is not so much needed for heating, because winter temperatures here overnight go down to 2 - 5 degrees Celsius, but climb to 18 - 24 degrees by mid-morning. Our inside temperature never drops below 18 degrees with no heating. The main benefit is keeping summer heat out. Daytime temperatures average in the mid-thirties in summer, but increasingly we get 4 - 5 week-long heatwaves coming in from central Australia and that is when we need our insulation, airconditioning and fans. On hot sunny days we run the big airconditioners all day and turn them off at dusk and the house stays cool with the fans on for circulation.
We have an 8kVA diesel generator with a 1500 RPM water-cooled Yanmar engine. It uses about 2 litres of fuel per hour and we hardly ever need to use it. The SP Pro starts it automatically once a week for 15 minutes just to keep it happy. It will also automatically turn it on to support the batteries if we draw a lot of power (say if we turned on the oven, dishwasher and the big airconditioner all at once - so we generally don't!). It comes on automatically if the battery state of charge drops to 60% during prolonged cloudy/rainy days. If I am around and the battery gets down to 70% I sometimes turn it on manually and run it for an hour or two just to keep the system topped up. Generally, even on cloudy days, because we have 10kW of panels we produce enough to cover our background daytime power usage (around 0.6 kW) plus a bit more to trickle into the batteries. We deliberately oversized the number of panels to achieve some power even at low levels of efficiency.
When we designed our rainwater harvesting system I looked at the price per litre of storage for concrete, polyethylene and steel tanks. We chose a Rhino steel tank with a food-grade PVA liner and I thought we might need a 90,000 litre tank to avoid running out and having to buy water ($125 for a 13,000 L tanker-full). The tank was so cheap for another couple of hundred bucks we upsized to the 130,000 L at about $9000. Our roof area on the house, garage and shed is so big it is full almost all the time. Best decision ever - plenty of spare water for firefighting, we use a multi-stage particulate and UV filter and its like drinking an unlimited supply of pure bottled springwater.
Hi Juxx0r. To expand on what I tried to make clear in the article, we designed the house to be as energy-efficient as possible, to complement our power system and to fit in with the micro-climatic conditions of our location. To address the issues you raise, we time the start of our heat pump hot water system for the hottest part of the day, but the rest of the load shifting is behavioural. We like to keep the inside of the house within the range of 20 - 24 degrees. In winter we hardly need heating because the insulation and low-e glass keeps the temperature around 20. If we want to warm the bedrooms before sleeping, the 2.5 kW inverter units draw about 1 kW of power and we put them on for 20 minutes then turn them off. During that time we use the ceiling fans on low speed in reverse and that helps spread the warm air.
In summer we close the windows at 7 am and if the outside temperature climbs above 30 degrees and it is sunny we can run as many airconditioners as we like from the AC current generated by the system, while the DC current usually charges the batteries to 100% by mid-morning. We turn the airconditioners off in late afternoon and open the windows when/if the outside temperature drops below the inside temperature.
The other intelligent load shifting comes by learning how to live off-grid without killing the batteries or unnecessarily running the generator. We try not to use appliances like the oven and (heat pump) clothes dryer at night or on protracted periods of overcast days. We have programmed the SP Pro inverter to come on to support the batteries if we do want to use heavy load-drawing appliances for an hour or two. We have a combined inverter electric / gas cooktop and a gas BBQ both working off two 45 kg gas bottles and we use mainly gas at night, but use electricity for cooking and boiling water during the day. All the lighting is LED and is all dimmable so we use very little power and get the lighting levels just how we want them. We have 3 fridges because we use them for different things and we have catered for that in the design.
We live a comfortable, modern lifestyle because we have designed the house and the power system to work in harmony and we have made the capital investment to build it and reduce our on-going operating expenses by living happily within those parameters.
26kWh per day average electricity usage seems to be really high for an efficient home.
We use 10kWh in an all electric home and pool. 3 person household. Our water heater is just a very good insulated electric water tank. We also have 5.5kW solar installed.
To see the arguments for and against the abovementioned Arvio supercapacitor really being a lithium titanate battery, visit this thread on the Australian Electric
Vehicle Association forum. http://forums.aeva.asn.au/viewtopic.php?p=67082#p67082