To be honest I decided to address how the output of individual collectors drops as the solar fraction increases for solar hot water systems, as I was working on a recent F Chart analysis for an upcoming project.
Solar thermal collectors must behave as wellpaid employees!
Therefore the owner of the system has invested initial capital in any and any collector, just after all. Normally, the energy output per collector, often referred to as the collector yield, is measured in million British thermal units over the course of the year. This metric is very important as the best designed systems must have any collector working as hard as it can. So in case a building uses 1000 hot gallons water per day and a solar hot water system supplies 500 gallons of that, the solar fraction equals 50 for that day. Fact, the solar fraction defined as the percentage of the overall load that is supplied by the system over a specific term. I’d say in case X number of solar collectors will supply half the load, 2X must supply the entire load, after all.
Basically the question is often asked, Why not take a 100 solar fraction all along hereafter?
This means the contribution from a solar water heater could’ve been zero for many days out of the year.
There’s nothing we can do about the weather. Of all, unlike conventional energy sources, we can’t just flip a switch to make the sun shine when we need it. For example, it can be cloudy or rainy for a few consecutive days. I would like to ask you a question. Well, Therefore if you can’t get 100percent, shouldn’t you choose as much as you can get?
That’s not what a graph would show us.
Going from 20 collectors to 30 collectors increases the solar fraction from 25 to 35percent.
We would see that as the general amount of collectors in a system increases, the solar fraction does seek for to be spending more money and have the performance per collector going down. Furthermore, any additional collector makes all the others a bit lazier. The graph would also show that as the amount of collectors goes up, the yield per collector steadily decreases.
Folks who design solar hot water systems above the sweet spot end up throwing away money. In the analysis above, I used similar hot water demand throughout, and changed the total amount of collectors. Note that the monthly solar fraction doesn’t reach 100 until mostly there’re 120 collectors, and the annual fraction is 89. Although, that’s not an ideal deal for the owner. Each collector produces 11 MBtu/yr which is 37percentage less energy than a system with a fraction of 35percentage.