Solar, like many other renewable energy sources is “infirm”. We cannot install a 1 MWp solar plant and generate 1MW at will any time we want. It purely depends on sunshine, and whenever sun is low – due to shadow or rain or whatever, the generation will be low.
So, when we design a solar system – what should we design with?
Maximum generation or minimum generation?
Conventional Load-Max wisdom says it should be built with lowest generation in mind.
That means, let us say we build a solar heating system for supplying 30 Lakhs KCAL a day (or roughly 3500 units a day – or roughly 1Lakh litres of water heated from 30 degrees to 60 degrees). In January in Chennai, it will require about 700 KW solar to generate the same. In April in Chennai, it will require only 550 KW to generate that..
Should we put a 550 KW or 700 KW? Conventional wisdom and load max principle will build a 700 KW, or even higher – like 800 KW with a factor of safety.
Is that right for solar?
Conventional energy sources are mostly variable – Diesel – we only pay for diesel consumed, and if the load is less, less diesel is consumed – at least lesser by some extent. Same with electricity, LPG, CNG, – any conventional fuel.
But, solar – it is mostly capital equipment, and very less – near zero – running cost. Putting up higher capacity means – we make it very expensive initially, and since there is near zero running cost, we pay for the full generation whether or not we use it.
So, if 800 KW is put up as capacity – in April – it will generate 20% more than required – but we still we pay for it. In January, it meets our requirements.
So, we essentially design it with a nearly 20-30% energy waste every year.
That is where our design principle comes in.
That is why we always have believed in hybrid systems – Hybri-Heat, where we design with optimum capacity. When the infirm solar generation is insufficient, the conventional heat source should kick in.
We design with a fundamental that “Not a KWHr of solar generation should be lost!”
That is what we call as SolarMax principle.