Appropriate Role of Solar Cells Solar Cells may be an appropriate way to make use of the already embodied fossil fuel energy in human skill and industrial manufacturing capacity to contribute to electric power production during the transition to declining energy availability. This is especially so: where small demand systems are remote from the grid. in sunny dry climates where low rainfall limits wood and other biomass production in sunny urban environments where solar cells can double as a roofing material. The greatest value from solar cells may be their role in forcing us to reassess how precious electricity is and the inevitable conclusion the we should use it only for high-quality functions such as small electric motors, lighting and communications. The increasing numbers of people living with autonomous solar power systems are the pioneers in a new culture of modest electricity use while continuing to participate in modern affluent society. The value of their actions may be far greater than any net energy gains or losses of solar cells.
(Excerpt from David Holmgren Page 98 of Permaculture: Principles & Pathways Beyond Sustainability)
When we first arrived at the house the only power supply was 100w of solar panels on the roof attached to 2 ageing heavy duty lead acid truck batteries. These were wired into two 40w halogen kitchen down-lights and a depressingly dim 4w cold cathode in the living room and as it was all 12v – a few cigarette lighter holes around the place.
Appropriateness We live on the peaceful side of the community buffered from the road by acres of forest, the other side of our property is undeveloped pasture. This remoteness puts us far away from the existing grid infrastructure – it might have been possible to get mains electricity connected – but it wouldn’t have been any cheaper.
When actually getting the system, my perspective was that solar technology was still a little green – as in not yet ready. It is an area of incredibly rapid development. I was right.
In the 12 months since we have had our system installed – the cost of the equipment has halved, mostly due to a now more generous government incentive and in part due to scale of operations and efficiency in manufacturing. However – what we have done in that year with that additional feed hasn’t left me feeling ripped off.
Designing for Us
David Holmgren uses the phase â€œdesign cul-de-sac. It would take us more energy to figure out, understand and integrate new components into an old system than it would to just do a new work right over the top. (we had a similar situation with the existing hot and cold water systems).
We planned to leave the old system in place to continue to power just the fixed lights. With this new plan in mind – we were eligible for the federal government rebate. One of the conditions of the rebate was that you must use an installer who is recognised by the Business Council for Sustainable Energy (BCSE ). Another is that you install a completely new system.
The terms of the rebate have changed significantly since our system was installed – see http://www.greenhouse.gov.au/renewable/pv/index.html
Their list of local installers yielded me about six likely candidates. A few of the larger groups such as Rainbow Power Company were consulted but quickly written off – I had a short list of smaller companies and continued to discuss my requirements and research with them until i’d exhausted all but one. Simon from SunSparks electrics. He is a mindful man who is raising money to build a school based on buddhist principles. He also sells Indian clothes at the local markets (we still discuss the ongoing system maintenance in passing at these local meeting places). I also trusted him, which I’ve come to find is a rare quality in the solar marketplace.
Working with him we drew up a sheet that would be submitted to greenhouse office outlining our expected power usage. This audit details; Every device you plan to use How much power it consumes How long you plan to use it Which devices you plan to use simultaneously what gets used seasonally And so on. This gives a very detailed awareness to needs and potential points of conservation.
A few patterns developed, one in particular to be aware of, anything that converts the high grade energy of electricity to the low grade of heat is a waste. A big one. Classic sucks of power like electric stoves (2,000w), hot water units(4,000w), air conditioning (a heat pump)(2000w), irons(1,000w), toasters(800w), electric kettles(600w) all consume so much power it would be ridiculous to run them on current solar technology. Thankfully they all have extremely low-imput alternatives.
So with our electrical desires laid bare we could move forward and submit our application for government assistance – it arrived two days later – the fastest approval in the history of the department. We took that as a good sign that we were on the right track.
We finally selected from the bottomless shopping cart of consumer electricals available for the affluent Australian: A small refrigerator (200w) A specially selected Fisher and Paykel Washing Machine (250w) Construction Power tools (100w ~ 1000w) Kitchen power tools (500w) Laptop Computers (~100w) LCD screen (150w) Water transfer pump (750w) A small stereo (50w) Lights, lamps and small batteries (100w)
At this stage we were running a gas fridge – it was one of our goals to kick that habit. It burnt through considerable amount of gas and chose to run out during periods of heavy rain so that the gas man would arrive, unload and then rip up our hand built driveway of sand and gravel with skids and swearing on his way out. Twice.
The fridge is our single biggest consistent load. It is trumped in peak power by the water pump but that is run infrequently and selectively so that we can pump when there is full sun and batteries are at capacity. The first step was to scale down, a full size 220L fridge for two people who intend to grow their own food is too much. The fridge effect is closely related to the travel bag effect – no matter how large or small it will be filled. We kindly asked for the return of my old bar fridge – a much more suitable size. We don’t miss the volume either – a fridge is a place where high turnover is to be valued. The freezer section is big enough for leftover soup and a try of ice cubes.
However to run this little cold box for five days without sun and without damaging the longevity of the batteries still requires a considerable investment.
The Batteries were installed first; they must be kept charged at all times so they come full from the factory. This means we could use them to power the tools used to install the panels and other equipment.
Don’t be fooled by their bright, cheery and green appearance that is 500kg of lead and acid. They have an expected lifetime of 10 years. I think moving them back up the hill for recycling will probably take 10 years off my expected lifetime, So I am treating them with the respect they deserve.
They have never been below 75% of capacity – they float (fully charged) most days of the year. Buying enough capacity in the first place means that we are not really deep cycling them, our pattern of light usage and consistent maintenance will mean we can enjoy them to their full potential.
This is the inverter and the regulator. The regulator is the brain of the system. It connects and monitors the inputs and outputs from all the different elements in the system. It provides feedback to us about our usage and status of the system.
The Inverter converts the 24v Direct Current of the batteries and solar panels to the 240v Alternating Current that is the standard for home electrical systems in Australia.
As well as containing large amounts of toxic lead and hydrochloric acid the batteries also vent explosive hydrogen gas. One of the conditions of getting government support for Remote Area Power Systems is properly managing this hazard. We have done this by building a vented box around the batteries that sit in a tray. We also have instructions for safe handling and hazards.
A special delivery from Japan.
It’s mostly silicon.
Beautiful….and then there is the Maintenance
Taking responsibility for the supply of your own electricity is empowering. But most of the work to support it is not glamorous. As well as a big financial commitment upfront there is regular ongoing maintenance.
Daily. It is important to put the regulator somewhere you can see and access easily. Checking how much power came in, how much was used and how much is stored is the fun side of the routine, I do it daily. Initially feeding back to others so that a lifetime of fat flow power usage habits can slowly change to a pattern that represents the natural flow can be challenging, but it is also very rewarding. We now both “know” days when we can use the big draw cards of power tools and water pumps. We have also learned at what time of day we can use those things so that the batteries get enough power to recharge again so they aren’t sitting low overnight. Weekly The regulator is a really amazing device. Once a month I take enter the data it stores into my laptop and log all the data so I can graph it like the one below.
But it can’t tell me everything. I also test each battery (there are four) and make sure they are all returning a similar voltage. If one battery is malfunctioning it will pull the whole system down while it tries to keep it balanced.
Monthly Once a month I am to check the specific gravity of the acid inside the batteries with an instrument called a hydrometer. This device gives the most accurate reading of individual cell health (their are 12 distinct cells in our system). It is used in correlation with an individual voltage measurement. For our system in our part of the world a hydrometer reading of 1.250 and a voltage reading of 2.22 represents a full, happy and healthy cell. This is the messy part (and the maintenance most often skipped).
These little guides tell me if I need to add any distilled water.
Half Yearly I check the panels for grime and clean them with a glass cleaner, tighten all their nuts and bolts and check all the electrical connections for wear and corrosion. I also do a thorough check for things like rodents in the battery box and mud-wasp’s making houses.
Why Bother? Ensuring that all this is done properly will return me 10-fold dividends in personal energy at the tail end the batteries life time. Which by keeping them floating in the top 15% of capacity is very far away still.
It also adds value to the investment – if I ever chose to sell – a comprehensive record of all the maintenance and long term patterns of usage allow a buyer to know what they are getting, and me to set a better price. It is also good for me – it keeps me responsible and continuously observing a big element in my increasingly complex system.