Living with solar as the main energy source makes one conscious of energy usage. This is particularly when living with solar stand-alone systems, even if you have power to spare. Lights are not left on unnecessarily. TVs are not simply ‘turned off’ from a remote control, let alone left on with the sound turned down. One buys only energy-efficient appliances. Dripping taps are immediately repaired. Less water is used for showering. Those living with solar off-grid typically use two thirds the energy of those with an otherwise similar lifestyle. Those living with solar stand-alone systems may use less than half.
Then visitors arrive! Lights are left on day and night. Showers are used until they run cold. Teenagers may leave the TV on all day whilst they use the computer to play video games – and left on all night. This is a hard one to resolve when living with solar unless there’s a stand-by generator. We partially solved at our Broome (north-west Australia) property by furnishing a cabin away from the main house. It had its own bore-fed solar hot water system. Bore water was also used for toilet flushing.
Visitors still wasted bore water but as we used 0.2% of our yearly allocation, and that unused flowed into the Indian ocean 300 metres away, their long showers were no longer an issue.
The cabin had a 60 litre Waeco chest fridge powered by the property’s 18 kW/day solar system. A three-burner LP gas top sufficed for basic cooking. Lighting was not an issue. The two 15 watt compact fluorescent globes gave ample light and drew little power.
Major problems may arise with long-term caretakers not accustomed to solar. Energy usage typically soars so battery banks are wrecked by being routinely flattened.. The only solutions are a hugely oversized system. Or an automatically starting diesel engined charging system. One then has to accept the fuel bill. Or have no caretakers.
Living with solar – our self-built house (north of Broome) was virtually 100% solar (generator battery charging was needed for less than a total of 50 hours over plus ten years.) The light fitting (top left) originally had four 50 watt halogen globes. We replaced them by four 7 watt Philips LEDs. They saved 172 watts and were brighter. For more details see Our All Solar House.
Puzzling solar input
Systems with adequate solar capacity may surprise new users by there being no more solar input during days of more than average sun. In most cases there’s nothing wrong. The solar regulator monitors the battery bank’s state of charge. When it senses the bank is fully charged it cuts charging right back and supplies only that energy being consumed at the time. That’s the time to do big loads of washing. Or those long-delayed welding repairs to the trailer.
People not accustomed to living with solar often worry that more energy is coming in each day than is going out. They ask if their batteries are somehow ‘leaking’. This effect too is normal. The cause is that energy cannot be turned from one form into another without some loss. The loss is in charging and discharging. The loss varies with battery type and capacity but is typically 15% or so. It is less so with AGM and gel cell batteries, and even less with the (still costly) lithium ion.
There virtually is none. The solar modules may need occasional cleaning in some areas particularly after a long dusty outback summer. Dry winds cause static charges that attract dust. Brief light rain turns the dust into mud but does not always wash it all off.
Fix both the dust and static issues by washing the modules with water and detergent. Then rinse with a bucket of clean water to which you have added just one teaspoon of detergent (it has anti-static properties). Use a squeegy to remove surface water – and then let the modules dry naturally. Do not rinse further, nor wipe dry, let alone polish. Doing so generates dust-attracting static charges. (It also helps to earth the solar module frames).
Apart from the above, solar modules need no maintenance. It is difficult to assess their usable life-span but some made in the1980s still produce about 85% of their original output. Total failure is very rare.
The reliability of a well designed and installed system is way ahead of the typical grid network. The output is also cleaner and the voltage barely varies.
Traditional batteries need topping up with water every six weeks or so. It is essential this is done or they will fail long before their time. Sealed batteries have a theoretically shorter life span but as few ‘wet’ batteries are adequately maintained it pays to use sealed ones. The lithium ion products have a long forecast life span but they have not been in use long enough in big solar systems to be sure.
Monitoring – an essential
Monitoring is essential. Many new owners maintain a daily log of energy in and energy out plus highest and lowest voltage. Most owners eventually settle for daily checking the battery bank’s percentage charge. The latter is all that is routinely needed as anything needing attention will cause significant variations.
The above text (but not layout) is taken from a page and a half of the current edition of the author’s Solar Success. The book is a total guide to home and property size grid-connect and stand-alone solar systems. The associated book Solar That Really Works! covers the design, installation and usage of solar in boats, cabins, camper trailers, caravans and motor homes.