Reducing fuel bills and increasing solar thermal output
avwFm87mDz2011-02-24T12:33:52+00:00Q: What is the best way to reduce my fuel bills by incorporating a solar thermal system?
A:Reduction +Reduction = Reduction This should come at no surprise to any of our readers but the single best way to save money on energy bills is by reducing your consumption. It is surprising to me still, to find that at least 90% of homeowners that purchase a solar thermal system to reduce their energy bills have made no other provisions for energy reduction. By simply changing shower heads and turning set point temperature by 5 degrees, a homeowner can reduce their DHW load by nearly 25%. When coupled with a solar thermal system they can approach, easily, a 75% reduction. If we look at a broader approach with a more holistic solution, the impact becomes greater, the payback goes down and the return on investment increases markedly. Take a look at heating systems for example as well. Many in the US require fairly high temperature setpoints in order to deliver high quality btus to the home. If we tie a solar thermal system into a home heating system that require such high temperature as 160-180 Deg F then we are sacrificing a considerable difference in collector efficiency. By reducing the temperature setpoint of the home heating system, installers can essentially get more BTU’s out of a Solar thermal system. The most important factor that determines collector efficiency (that you have any control over) is the incoming temp to the collectors, therefore the lower the incoming temperature is, the higher the output will be. In other words, you get more by requiring less. For example, a heating system in the North East Us that uses baseboard emitters requiring 170 deg F will see an average efficiency during the winter months of nearly 35% for Evacuated tube collectors, and much lower still with Flat Plates, IF the installer couples the system with setpoint reduction measures (i.e. outdoor ambient reset, lower temp heat emitters, radiant floor tubing replacing baseboard etc) then the total collectors efficiency can nearly double. This means MORE useable BTU’s!!
REDUCTION in Load and REDUCTION in temperature means REDUCTION in payback!!
How can I simulate the performance of my solar thermal system?
avwFm87mDz2011-02-24T11:17:04+00:00Q: What is the best way to use a computer simulation model for my solar thermal system? A: There are many types of software that help determine the energy output of solar thermal systems. We use Polysun Simulation Software, professional version. With this software we can effectively design small to large hot water and heating systems with a high degree of accuracy. Contact your SunMaxx Solar representative for a Polysun analysis of your home for a solar hot water upgrade at 1-877-SUNMAXX.
Setting your solar thermal system differential temperature setpoint.
avwFm87mDz2011-02-23T15:42:53+00:00Q:What is the most appropriate differential temperature for my solar thermal system?
A: The factory setting on our controllers is 12 Degrees. This will work fine but for northern climates it is better to have a delta T of 17 Degrees. This will allow the collector to heat up sufficiently so as to not turn the pump on and off early in the cold mornings. In warmer climates, say mid-latitude and below you can keep the factory setting at 12 deg F.
Keeping propylene glycol from freezing in my solar thermal system.
avwFm87mDz2011-02-23T15:37:27+00:00A: How do I prevent my glycol from freezing during those rare deep freeze nights?
Q: Your glycol, although rated for very low temperatures may be un-pumpable at a temperature higher than you expect. This can cause you system to overheat when the sun comes out in the morning. To prevent this you can activate the antifreeze function in your SmartMaxx controller. This function will turn the pump on as soon as your sensor 1 reaches a pre determined temperature, say -5 degrees. This will run only for a few minutes and then turn off, thus keeping your glycol above the un-pumpable temperature.
How do I determine the most appropriate solar thermal storage size?
avwFm87mDz2011-02-23T13:59:29+00:00Q: How to determine the best solar thermal storage size. A: Choosing your storage tank size is dependent on three things. 1- the number of ft2 of collector- for example we typically recommend any where from 1-3 gallons of storage per ft2 of collector, 2- the daily load profile (usage pattern) for example if most of your usage occurs in the early morning or in the evening, then you would not adjust your storage ratio. However, if your usage occurs more in the mid-day then you would reduce your storage ratio because you will be consuming that which you are producing, therefore saving energy can be a moot point 3- the required temperature. For example the colder the required temperature, the more storage you can have per area of collector. If you need some really high temps for baseboard heating then your storage ratio will be 1:1 or less. But if your required temperature is 100 degrees F then you can maximize your storage capacity with, say, a 3:1 ratio.