Browse Forums Heating, Cooling & Insulation 1 Dec 22, 2009 2:26 pm Does anyone know if its possible to operate four solar collectors with a 300L system? (Solaharts classic solar heater model). I have four collectors available to me, and it would be a shame to throw one away. Hopefully there's no restrictions in having four collectors cascaded in series. Any info would be great. Thanks, Steve Re: Four Solar Collectors on a Solahart 300L system? 2Dec 22, 2009 8:30 pm You really only need 2 collectors. How many people will be in the house? If kids, how old? What state do you live in? The 300L's are designed to work efficiently with 2 collectors.. if you don't use enough of the hot water produced from those collectors, the hot water will be expelled anyway (via the hot water relief valve). I'm in Perth and used to work for a Solahart dealer, we'd often have people ringing us in summer complaining because their system was dumping hot water. Solution: if you have a large tank and only 2 people in the house, cover one of the panels with shadecloth in summer, to prevent too much heat gain. I really doubt you'd need 4 collectors, no matter where you are. Oceanic with Nautilus upgrades. Handover 8 September 2010 Re: Four Solar Collectors on a Solahart 300L system? 3Dec 23, 2009 2:19 pm Might be handy in winter if you don't get much sun and want 100% solar hot water and no boosting. But I agree that it will easily overperform during summer. Re: Four Solar Collectors on a Solahart 300L system? 4Dec 23, 2009 3:41 pm The system is currently configured with two collectors, but hoping to never use the booster at all is what was driving the idea behind installing four collectors. We're not a big family, and dont need that much hot water, but having enough collector capability during winter is what I though would help. The water loss from the overflow valve is quite minimal at the moment, but we have that directed into the pool to save water. I take it with four collectors there would be more overflow? steve Re: Four Solar Collectors on a Solahart 300L system? 5Dec 23, 2009 4:08 pm You may end up with twice as much hot water in summer i.e. another 300L. Re: Four Solar Collectors on a Solahart 300L system? 6Dec 23, 2009 6:12 pm SteveH The system is currently configured with two collectors, but hoping to never use the booster at all is what was driving the idea behind installing four collectors. We're not a big family, and dont need that much hot water, but having enough collector capability during winter is what I though would help. I don't think you would achieve that aim in mid winter even with 4 flat plate collectors. You would probably get some benefit in the shoulder seasons (but then there is the issue of double the excess hot water in summer.) It is related to the efficiency curves of plate plate collectors. The efficiency of the flat plate collector decreases with increased delta T between the air temperature and the hot water temperature (delta T is at its highest in winter) and also decreases with lower solar insolation (which is at its lowest in winter). The efficiency of the plates decreases so much in winter that there is insufficient useful heat for long enough on each day. Typical SHW efficiency curve equations can be seen here. http://www.sustainability.vic.gov.au/re ... ers_v2.pdf (See table at bottom of page one.) In cold weather and low solar the panels shed heat nearly as fast as the incoming solar. (This is for Melbourne - can't comment on other locations.) If you want me to post some rough calculation please advise. Re: Four Solar Collectors on a Solahart 300L system? 7Dec 23, 2009 7:08 pm With a collector efficiency of 45% and a 2.23 kWh/m2 (Adelaide winter insolation) you could generate about 140L hot water with 4 plates. Re: Four Solar Collectors on a Solahart 300L system? 8Dec 23, 2009 9:07 pm dymonite69 With a collector efficiency of 45% and a 2.23 kWh/m2 (Adelaide winter insolation) you could generate about 140L hot water with 4 plates. I don't think you can just take an assumed efficiency and multiply it by the total daily average insolation. The efficiency of the collector will vary over the day from zero up to whatever the max efficiency is - this is because the air temperature and solar insolation varies over the day varying the efficiency. So when the sun first come up the first rays that hit the plate they might heat the plate but they won't heat any water up to 65 degrees - so it is only the sun in the middle of the day that is going to do any real work heating the water. Re: Four Solar Collectors on a Solahart 300L system? 9Dec 23, 2009 11:02 pm I calculated it at between 90 and 140 litres on an average July day in Melb for 8 sqm panels. The upper one aligns pretty well with dymonite's estimate. This is for the higher efficiency flat panel. For the mid efficiency panel it would be less (70 to 110). The figures are higher than I thought they would be. There are still going to be days of below average solar and temperature when there won't be any solar hot water. And summer overheating will be an issue. Re: Four Solar Collectors on a Solahart 300L system? 10Dec 23, 2009 11:15 pm Efficiency info based on tech data for actual collectors. Graphs are available showing efficiency versus Ta-Tg gradient. 45% is about water is 60 and outside temp is 10. Ground water temp assumed to be 13 deg. The insolation figure is daily total i.e. 2.23 kWhr/m2/day not instantaneous irradiance. I looked into it a few years ago and my conclusion was to just build a carport that will support panels and get a system installed separately. The company I looked at had… 1 6483 Once you know the basics, the rest is easy. Read my post in the thread linked below. viewtopic.php?p=1919271#p1919271 2 19521 It's all about wireless, self install now. The cost/benefit of wired setups for the house are no longer what they used to be. Lots of wireless options. Eufy, Arlo and… 2 9797 |