New Solar Tthermal Design Help

solarbeam

I live in Massachusetts. I am installing a one new style parabolic solar concentrator (<a href="http://www.solarbeam.us/">www.solarbeam.us</a>) to supply domestic hot water, space heating, and pool heating for my home. The concentrator puts outs out 13kw an hour of thermal hot water in full sun.



My concept is to send the primary heat to a 120 gallon stainless steel solar storage tank for domestic hot water, this tank with an internal heat exhanger. In the winter, once this first tank is satisfied, then send additional hot water to two 120 gallon storage tanks that will somehow supplement my current oil fire boiler for winter space heating, I have radiant baseboard heat now. In the summer, I will also purchase a pool titanium heat exchanger for the 28,000 gallon pool, and direct pool heating after the DHW is satisfied.



Questions:

1. What are better. Internal or external heat exchangers.

2. Tell me about the conduit for piping from outside collector underground to home. I see the double 1" stainless steel tubing with insulation and a wire. Should I put this in a 4" PVC conduit for added insulation, the run is 125 feet. I was told to stay away  from PEX.

3. What size and style pool exchanger is recommended.

4. I was planning on two 120 gallon additional solar storage tanks for my space heating needs. I was told multible tanks are better than one big one, as it becomes to hard to heat one large tank?

5. Are stainless steel storage tanks worth the extra money?



Thanks



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hot_rod

good questions

with pros and cons. External heat exchangers allow you to size exactly to the load and condition. They are easier to service and flush if needed and can even be removed and boiled out. They also allow you to purchase a less expensive storage tank.



They do cost you another pump, additional piping and insulation and more labor to install.



A tank with an internal HX cleans up the job as far as piping etc. Multi coil or multi energy tanks puts all the HX in one footprint. Most are very well insulated and constructed. look for a brand with a lot of surface area in the HX, and multiple locations for sensor wells.



Yes I would put the underground piping in a PVC sleeve. It needs to be glued and water tight.. It would be nice to have at least 1" of insulation. If you use the insulated stainless line set consider a foam extra layer as you slide it in.



Some installers also spray foam the PVC condiut right in the trench for extra insulation value.



The pool HX is sized based on your application, look to the manufacturers specs. Bigger is better with solar HX as you do not always have the high temperature that a boiler would provide. You might consider a plate pool HX as they offer more sizes and options. Check with some of the online HX sizing programs.



If you stay below 120 gallons you do not require ASME listing on the tank. Prices really jump over 119 gallons.



For domestic water in some areas stainless out lasts glass lined steel and vice versa. It really depends on water conditions in your area. Ask the local installers or suppliers which type have a better track record in your area. With a glass lined steel tank, keep an eye on the anode rods to assure a long life. Some brands install dual anode rods for extended service.



Is it possible to configure that collector as a drainback? That would address overheating potential. You could also use a plain steel tank as the drainback and heating storage vessel all in one.



Controls may be the biggest challange. There are numerous solar controls with multiple delta T function outputs. These used with 3 way zone valves allow you to shuffle input and loads.



There are many ways to pipe a system like this, you need to draw it out, list priorities, determine how automatic you want the system to be, and consult your bank account



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