Some Solar Thermal Systems
DHW - Domestic Hot Water, showers, clothes washes, dishes etc..
Heat Exchanger: A way to move heat from one isolated system to another.
Air Handler: A central device used to move heated or cooled air in a home.
1. It has near perfect orientation and access. The goal will be to supply almost all the DHW requirements and 50% or better of the space heating. The current heating system is an oil fired hot water boiler. DHW comes from a coil into the boiler and the space heating is hot water baseboard.
The system is now complete and operating fully. Tweaking remains. SDHW has been operational since August 09 and the tie in to space heating was complete on 01/13/2010. Initial effectiveness seems promising. A custom 500 gallon Stainless Steel tank integrated into the Summer time AC system provides solar heated air to the house in front of the oil fired hot water baseboard system. The array is 200 tubes on the barn and the Glycol loop runs underground to the storage in the basement. Glycol loop was chosen due to the inability of running pipe meeting drainback requirements. Data will be provided for the first complete year interval on 01/2011
UPDATE 11/02/2010... The oil burner was shut down in May and sat until October. Oil was bought in September. 473 gallons filled the tanks making that the usage for the year. Normal usage is about 800 gallons. That is pretty good considering the space heating part of the system did not go on line until the second week in January. The tanks had been depleted to 5/8 full at solar space heating start. It is expected that running this year, the solar space heating for the entire heating period, will save an additional 1/4 tank. My guesstimate for the new whole year oil usage with all solar active, will be in the 350 gallon ballpark, or about a 57% reduction, typical range 55% to 60% depending on sun and temps..... not bad at all... pretty much right on design estimates....
2. It has near perfect orientation and access. The initial goal on this home will be to supply 50% or better of the DHW requirements, while allowing for easy system expansion into the space heating load down the road. The current heating system is a high efficiency oil fired hot water boiler. DHW comes from the boiler through a separate heat exchanger tied to an external 40 gallon tank. Space heating is accomplished through a separate liquid to air heat exchanger and air handler.
It features a prototype DPDB system using 2 SFB-30's. Storage is 80 gallons for DHW use. Collector mounting angle is 60 Degs for Winter optimum and reduced Summer over heating. Starting and ending storage temperature is tracked by owner each day. Top temperature in the storage tank so far near the end of January was 194 DegF!! A thermosyphon chill chaser hydronic baseboard section will probably be added to keep the maximum temperatures lower during heating season virtually eliminating the possibility of overheating while reducing oil usage further and increasing solar system efficiency.
3 The system uses a multi-tank DPDB concept. Total number of collectors is seven, 30 tube units (210 tubes). Storage is at a absolute minimum of 33 gallons per 30 tube unit. As a result, storage temps will rise very quickly in the presence of solar energy. Collector mounting angle is at a steep 67 degs. The storage is across three separate pressurized tanks so stratification will be quite good. Flow rates will be kept under .5 GPM per unit collector. The whole system will provide SDHW and radiant heat with an on demand oil fired unit providing backup. Weil Mclain indirect heaters are being used in part. Sun access and orientation is excellent.
The owner has already realized 200 DegF in Dec. and hit 230 DegF in March as his top reading. Stratification runs as high as 76 Degs from hottest to coolest at the 230 DegF level. Temperature is now being limited to 220 DegF by using a basement high mass radiant floor loop which is available. Owner is tracking several data elements going forward including start and end of day temps, backup oil burner runtimes and solar run times to name a few. This system was almost completely done by the owner with guidance from www.WeAreSolar.com. The end result is nothing short of an outstanding professional job in all ways!!!
An 8th collector has been added to bring the total from 210 tubes to 240 tubes. Storage has been increased from 240 gallons to 320 gallons. Stratifications as high as
120 degsF have been obtained. Data for 01/01/07 to 12/31/07 will be coming in about a month. The 8th collector was just added so it's impact on the first years data will be negligible. The
additional 80 gallons of storage was added on 04/21/07, so its impact will be 1/3 to 1/2 of what it will be for the coming years data, I.E., 01/01/08 to 12/31/08. At this time it appears there will
be a 65% reduction in oil usage for the 07' year, comparing to pre-solar base years. It is guesstimated that with the 320 gallons of storage and the 8th collector, a 75% reduction should be
achievable comparing to non-solar base years. Data will be presented when in hand.
PSD data for January 2, 2007 just in for #3 Lehighton. SOD tank temp 95 DegF, EOD tank temp 185 DegF, net gain over period 180, 000 Btus at an average collector output temp of 150 DegsF. That does not even include hot water loads or heating loads over the collection period. An average PSD yield of 25700+ Btus's per 30 tube unit!!!! Outstanding numbers at a high temperature!!!
Here are the average temps (DegF) for the final storage tank in the #3 Lehighton house. There are 4 - 80 gallon tanks and this is the #4 tank, which is the hottest. I used this tank because this tanks water is what is presented to the DHW and the radiant heating systems in reality. Differences in total year averages between monthly and seasonal temps are accumulated rounding differences only. You can look at either one as valid. This coming years data (01/01/2008-12/31/2008) will represent the system in its final configuration at 320 gallons and 8 collectors through the entire period. The total fuel reduction for the 2007 year came in at 65% due to a very, very cloudy November and December.
The data is in for 01/01/2008 - 12/31/2008. The short version is that the savings are about the same as last year, 66% or so. There was increased load in both the DHW and space heating, off setting the full year at 8 collectors and the 320 gallon storage capacity. November and December were once again very, very cloudy... I think even worse than last year. I see a disturbing pattern emerging in the sun and cloud levels. They seem to occur much more in clumps and generally less sun over all in the Winter for lake effected parts of the Northeast. This would be in line with the predictions for global warming, yielding more extreme drought and flooding conditions sometimes in close proximity to each other. Wet areas get wetter and dry areas get dryer, etc... the weather in general becoming less uniformly distributed than in decades gone by....
4 It is a DPDB system with 320 gallons of storage. However, the collector to storage ratio is more aggressive than number 3. This is due in part to the larger home size and the longer piping runs. The array as shown, is a ground mount in two rows of 5 collectors totaling 300 tubes, located on the North side of the home. The conventional heating system is Propane forced hot air. Solar energy is added to the heating system via a liquid to air heat exchanger located in the return air duct just prior to the furnace. There are no heat exchangers for the DHW or on the array collection side, the primary advantage of DPDB. Data will be posted as available.
Array is located 37' (to top) from the basement storage on the North side of the house. The top of the array is actually level with the top of the house. (4) 80 gallon tanks are used for 320 gallons of potable water storage. System design is DPDB so no heat exchangers or anti-freeze are used, except for the space heating hot air exchanger. A single computerized pump solution is used to overcome head issues. Flow rate is 2.5 GPM to obtain a high level of temperature stratification across the four tanks. Collector angle is about 67 Degs for Horiz.. Array is wired for web based Data collection down the road. The owner put a tremendous amount of work into this system, as well as extended patience. System has been operational about a week. This shot happens to be on the Winter Solstice, a nice sunny day after a very, very cloudy end November and beginning December. Merry Christmas and a happy new year!!!
5. It is a simple closed loop Glycol using a SS flate plate heat exchanger. The solar pre-heat tank is an 80 gallon Whrilpool electric used as storage (electrically disconnected). The solar array is 2 - 20 tube 58mm x 1800mm evacs mounted at about 65 Degs with "Elephant Racking". System went into operation at the beginning of July 2011. The system is functioning well. It feeds a 50 gallon electric water heater for backup.
6. This is a 60 tube 80 gallon DPDB SDHW in Hawley. It is a vacation home which makes it more difficult in many ways.
Standing losses of the backup electric water heater are more of an energy load than the "real" load itself. An alternative pathway for the solar loop was initiated to include the backup electrics (electric backup and de-superheater tank) which keep them hot when the water heater timer has the backup in the off mode. When the backup heater is turned on, the backup tank is already hot allot of the time reducing usage accordingly. The timer was constructed for a 7 day cycle. BTU numbers are not available for this site due to the vacation status.