Is it worth installing a solar system?

Introduction

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, because of the carbon emitted into our atmosphere

I just looked on my phone at our solar system data for the combined 2 buildings and the stats say we are saving approximately 1.2 tones of carbon dioxide per month with our solar system.

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?

Solar systems for buildings

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 15K watts of solar on the roof.  We use the energy during the day to run our lights and machinery, it 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. 

Solar systems in motorhomes and caravans

Fortunately RV's mostly have a house battery, so the expensive bit is covered, 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 our own brand of solar fridges to NZ, our solar fridges were designed for the tropics so they are super efficient in New Zealand's climate. At the time 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 solar system designed for a specific purpose will work great as long as the energy demands stay the same. The system must be designed to handle the worst case scenario and not crash. A system that fluctuated in energy use is harder to cater for and 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, in this case we would have a solar system with a backup generator that starts automatically when the battery reaches a pre-set 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 the bus, and I know it is still going strong now.

We will recover the costs of the solar installation on our workshop and warehouse within 4 years and then our energy will be free for another 20 odd years, and when we produce more than we need we 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? 

It 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.