Is it worth installing a solar system?
Fossil fuel is just solar energy which was harvested naturally millions of years ago and conveniently stored under ground by the planets natural processes. Humans have been digging it up and using it since we learned to make fire. It is a convenient transportable energy source compared to solar energy, and you can use it at night, but we cannot continue doing it for ever more.
Is it worth installing a solar system?
That question immediately raises many more questions in my head, so I have answered these questions below from my own perspective.
What is the purpose of the solar system?
If the purpose of the solar system is to generate energy for immediate use, then solar energy is very useable and it is a no brainer, a solar system makes perfect sense. However the sun does not shine at night.
The image above shows our workshop and warehouse with 15Kwatts of solar on the roof. We use the energy during the day to run our lights and machinery, it all makes a lot of sense, we don't use energy at night because we have gone home. If we want to use solar energy at night we need to store it first, which is expensive because the cost of batteries is high.
Fortunately RV's have a house battery anyway, so no extra expense is required, and most appliances inside the vehicle will run on a combination of gas and 12 volts, The high energy items use gas and the low energy components use 12 volts. Refrigeration in motorhomes has traditionally been done using Ammonia fridges, also known as 3 way fridges that run on 12 volts, gas and 240 volts. Ammonia fridges generate heat to make cold and this method is extremely inefficient. it uses about 10x more energy to do the same job as a compressor fridge, it would not be feasible to run Ammonia fridges on solar energy, because they are too energy hungry. About a decade ago we introduced solar fridges to NZ, our solar fridges are designed for the tropics to be as efficient as possible so they can run on solar energy.
We tried various ideas, and I experimented with running a variable voltage compressor freezer directly of solar energy without a battery, which meant cooling down the freezer as much as possible during the day and storing the cold energy throughout the night without running the freezer, but this method proved to have large fluctuations in temperature, so we abandoned that idea. The best method we found was to have a solar system big enough to charge the battery and run the fridge during the day and yet have enough battery capacity to run the fridge all night long as well.
So is it worth installing a solar system?
Clearly, a well designed system which uses or saves the energy for a specific purpose and consumes a consistent amount of energy over time is a good project to run on solar energy, and fridges do just that. A system that fluctuated in energy use needs to be big enough to work well when the energy demand is high day or night and the rest of the time it is an expensive bit of equipment sitting idle with nothing to do. So pick your project carefully.
We have custom designed systems that use a combination of solar and fossil fuels because the customer demand fluctuates, an example would be an off grid Bach that is used excessively during summer periods, when all the whanau come to visit at the same time, the demand on the solar system would be high during that period, and that is just the time when it should not fail, we designed a solar system with a backup generator that starts automatically when the battery reaches a preset discharge threshold.
Is it going to save me money?
Running a fridge on solar energy will cost you absolutely nothing after initial layout and the battery should be good for about 7 years, I converted a bus and fitted a solar system and fridge in that vehicle, the fridge ran nonstop free of charge for 6 years till I sold it, and I know it is still going strong now.
We will recover the costs of the solar installation on our workshop and warehouse within 2-3 years and then our energy will be free for another 20 odd years, and when we produce more than we need we will get paid for it because it is grid tie. I am amazed that there are only 2 businesses on our entire industrial estate in Silverdale that have a working solar system. It is incredible that there are acres of industrial roof real estate and no one is utilizing the space.
What benefit do I get out of this expensive installation?
That all depends on on your perspective, how do we value something like a solar system? I think there is a certain feel good factor in getting something for nothing and generating green energy, there is a long term cost gain, and the way we have been using energy so far has not been sustainable. It's a bit like going on a diet, nobody wants to do it but actually it's a very good thing to do, and there are real long term benefits.