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Forum Index : Solar : Solar GTI input Maths
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| Phil23 Guru  Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
One of out local identities did something very similar on his Solar Boat. Have spoken to him personally & he mentioned having aluminium tanks fabricated & the panels attached to that. The Setup created both his hot water & cooled the panels to sea water temp once heating was completed. Dunno is any heat exchanger was involved or not. Gets a brief mention here & here. Cheers Phil. |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I just added 2 140 mm fans with Oztules control board to the top of my 5KW Zeversolar GTI. The GTI is in a shipping container that is airconditioned, previously it was showing temperatures in the mid 50's and according to the manual, it starts to reduce output at 45 degrees. Since the fans are on there it now does not get above 35, I don't know if it has much of an effect on the power output but I am sure the lower running temperature won't do it any harm.   There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
I just put together my auto fan switch yesterday. Small 40oC temp switch, relay and a tiny transformer. The switch will do 5A but as I want to put it on the side of the inverter I didn't want 240 running through it. I used the little 9V 300ma transformer ( $1 ea from fleabay) to run through the switch and go to the low voltage side of the SSR to switch the 240. Mounted it to the side of the inverter with a bit of heat paste and duct taped it firmly in place. Seems to be working well and exactly as I wanted. Don't think It will be doing much today though, too much cloud. Also got my Voltage monitoring relays. Going to use them to switch on the hot water heater when they detect higher line voltage from the solar feed. Cheap solar controller which should work every bit as good as anything else and better than a timer. If there is no solar feed, like today being cloudy,the heater will just operate off the off peak as normal. These things look like they will work really well but prove the old adage about only read the instructions as a last resort. Although they were written in perfect English, They were confusing as hell and the circuit diagram was flat out wrong. Wiring as the suggested had the load directly connected to the supply on both poles which meant it would have run all the time and the relay was useless. Putting the instructions aside I followed the markings ion the side of the unit and had no trouble with it. pretty straightforward, just pick the contacts you want. The programming instructions make it look like one had to program a space flight computer in Unix. Powering the thing up and going through the menus was very straight forward and logical.... Completely opposite to the printed instructions. Thank god. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I have got all mine inside, I know GTI's are designed to go outside but I prefer inside. My fans are and control are powered by a 12V plug pack. The control board above comes on gradually so the fans only run as fast as required. This the control PCB.  Further details here. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
I prefer having the inverters indoors as well. Makes it easier to keep them out of the sun which is a big factor in cooling in itself. Lack of water around connections is another big plus to me. The variable speed of the fans in your design may be an asset in some instances. I thought about this using different temp switches and activating relays with different resistances to the fan. To me seemed overkill. I have a speed control on the 240V fan I'm using atm and have found a setting where it supplies adequate cooling at low speed and minimal power consumption. Turning it up make no diff to the inverter temp as the ambient air is usually pretty warm here being summer anyway. Spose there are trade offs to every approach lot easier for me just to wire some components together than make up a board and put all the components on it. If I go to 12V fans, the power they use is so minimal I won't be worried about saving a few watts slowing them down. As mentioned, they can be pretty hopeless with resistance and backing them off makes that far worse. Not really worried about noise either. They are in the shed and the car radiator fans in the window make a hell of a lot more racket. I'm going to get some smaller radiator fans next week and see of I can set up the ducting with the tub. Other thing I thought of was using some large PVC pipe Cutoffs and mounting the fan in that then using a heat gun to shape the other end rectangular to fit over the inverter. Used to make a of of ducts like that back when I played with fast cars for cold air intakes. Worked well with large pipe and as cheap as chips too. If I can do that I'll hook them to my broken panels that still seem to work great and have a totally self sufficient system with no control at all. Just direct wire the fans to the panels in series. Leave one in the window and the other blowing on the inverter. Brighter the sun shines, more power the inverter makes, More power the broken panels produce, the faster the fan spins. I'll probably get some much lower temp switches and use the rest of the setup I have now for turning on lamps to keep frost off my veggies in winter. :0) |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I grew up on a small crop farm and we used irrigation to stop frost. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Never heard of that one but until a few months back, I was strictly a city boy! What I have heard of and seen , particularly in the US, is burning loads of Diesel or oil in " Smudge pots" to keep the air warmer over the fields and Giant fans powered by 400 CI motors blowing the air round to stop it settling and crops freezing. Don't know how that would go with wind chill factor but must work. Running Big petrol engines all night for months at a time must be real economical to do over 20 or 50 acres of land! |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
I was just reading up on a few articles I found on panel cooling. Different researchers have found up to 24% gains in efficiency of panels. Keeping them 10O cooler it seems can result in gains of over 10% in electrical generation. 9-13% efficency increase seems to be a common and practically doable increase. I had no Idea they had that much fall off due to heat. Explains why my 2Kw arrays do 1500w on a good day! Read a lot of things this morning on this but the take away was in the last paper. It said that while active cooling could result in a net efficency gain over the power used to cool the panels, the real gains were in the use of hot water. Said it was not feasable to create domestic hot water as that had to be over 65o to stop bacteria and that was too hot for the panels. The said the heat generated was ideal for space heating. The catch was by definition, there was less heat available in winter when it was the most needed and the panels would require much less heat removal to start with. Yeah, never as simple and straight forward as it sounds! Haven't seen anything on using panels in a Co-gen setup, only for the increase of electrical out put. I'm sure my panels lying flat on the tin roof will be suffering a lot of efficiency loss having little space for airflow behind them which was noted in a couple of papers I read. Having the elevation of the normal rack mounting would be a good thing from this POV. If we take an increase of 10% increase in power through cooling by whatever method, what's the real gain? 25W on a 250W panel. 500W on a kw array. Is the cost to cool the panels through whatever method be it passive such as heat sinks under the panels or active such as water on the top or back of the panels, worth the cost of materials to do it as well as labor, potential failure points and maintence? Comes back exactly to my rule of solar efficiency. Don't go to any effort trying to make what you have perform better, just throw a couple more panels in the array and don't count them and you will have a very efficient system... especially when it's overcast. 2 more panels on your 5KW array and you have well overcome any and all losses due to heat with minimal cost and zero maintence. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Water your garden with water that is say 15 degrees will warm it up to well above freezing temperatures. It would be easy to sense the ground temperature and apply water as needed. The easiest way to over decreased output of panels is to add more. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
In most cases (esp with the current prices) I'd say add more panels is the simplest answer as well. I even thought about doubling the panel array size for winter conditions and simply not using half during summer (just switch them off!! 0 Seems a bit wasteful but as its going to be offgrid and overcast is going to be the issue mostly, design for worst case and enjoy he excess when available One case I could see for active cooling is where space is limited and plenty of water is available, like boats We hired a houseboat for 2 weeks and it suffered solar availability in that the panels were flat and space was limited (top deck was used as party/deck space), and often had to start the motor just to get power (limited battery capacity didnt help) |
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| Mulver Senior Member  Joined: 27/02/2017 Location: AustraliaPosts: 160 |
Quick update. So I bought 9.5kw of panels a while ago. Managed to get 4kw mounted and connected to existing GTI. It should be 5kw so 2 panels missing per string because there is a solar HWS in the way that will eventually be removed. In the end I’ll have 5kw (2 strings) of 250w going to my 4.2kw inverter and 6kw (4 strings 1500w each) of 190w going to my 5kw inverter. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Price of panels seem to be dropping a lot lately, saw 30KW of 250W panels on Gumtree recently for $30 per panel and cheaper for bulk. So there will be plenty of us working out how to add more panels. The new version of the GTI regulator I am working on will include current limiting based on battery current. But I think it may be a good idea to have the option to control PV current. It would be easy to implement with hall effect sensors to keep the GTI happy. However, your proposed setup sounds fine Mulver, is there no way to keep the SHWS? You need a much bigger surface area of PV to get the same amount of heating. My SHWS ended up dead cold earlier this week for the first time due to rain and the power to the circulating pump was accidentally unplugged. It would not have gotten that cold if it was getting heat directly from the sun. I have my charge controllers setup to turn on the heater in the HWS when there is excess power but there was none with the few rainy days we had. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
saw 30KW of 250W panels on Gumtree recently for $30 per panel and cheaper for bulk. Wish I had seen that. Would have bought the lot! Panels have been a bit rare around my way of Late. I have been looking at vac tube HWS but still a bit unsure about their abilities. They seem to be over efficent if anything in sunlight but do they do anything in overcast Conditions? In clear weather, what is the " required" Number of tubes Required in Sydney for a 400L HWS? Far as Hydro based or PV based HWS, The PV sure has it as far as connection goes. I'm thinking so far that about 4Kw of used panels is going to give me the 8-10 Kwh of power I have been monitoring my system using for the majority of the time when any solar is going to be working. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I am not sure if the evacuated tubes are any different but SHWS rely on infrared light which does not penetrate cloud very well. PV panels make use of ultraviolet light more than infrared so they still are able to make some power under cloud. With thin high cloud, I have seen my panels making very little less than on a clear day. If the weather is good at least here in QLD you can expect an average of around 4.5 times your 4 KW in a day so about 18KWH. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Well I missed that comment; but I do understand the term "No Plummet Please" |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Some of my writings are no better. Years ago when I was a photocopier tech the Japanese manuals were not much better with things like "attack the sorter to the copier". There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
>> In clear weather, what is the " required" Number of tubes Required in Sydney for a 400L HWS? You will need 40-50 vacuum tubes for that size cylinder, assuming 3-4 persons in the house, They are efficient and work better than flat panels (for the same net surface area) especially in very cold climates and somewhat immune to frosts as the water is contained in the top well insulated heat exchanger. Like any thermal panel they don't work so well in heavy cloud. Downside of tubes, you cannot build them yourself, I have 10sqm DIY flat hot water panels I built over 10 years ago running two separate hot water cylinders, copper pipework, copper foil soldered to pipes painted black, alloy cases, poly-carbonate glassing, supplies >90% of our annual household hot water, payback on materials 3 years, you cannot beat free hot water... Doing it today, I would install PV panels and power the element with 240 AC via a mppt DC to 50HZ converter. Get 2nd hand PV better still; trouble here in NZ, I have never seen 2nd hand panels for sale other than the odd 1 or 2 off a caravan or similar. Downside takes a lot more roof space than thermal. Cheers Mike |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Thanks Mike! I had it in my head that the tubes were a lot more efficient than that. I didn't think anywhere near that many tubes would be required. Really was just interest, I have 16kw of panels atm with another 5 kw to get on the roof and wiring is a lot easier than Plumbing..... and cheaper too! That said, I'm always keen to play with things myself and learn because I find there is a lot to learn in practice that often the parroted mantra's go against or don't cover. IF I found some tubes Cheap I'd like to get some to play with and learn about them. You can always tell the age of info on solar water heating. The older info says solar PV is inefficient and advise using direct water heating. Eventually the advise turns to PV Is the DC MPPT converter the one you did a couple of Vids on? ATM I am using a Voltage monitoring relay that switches on when the solar GTI raises the line Voltage. That goes through a PWM controller to take the input down to about 1500W to reduce the load and spread the heating time which helps with reducing the High line voltage that is in my area. Next Summer I might have a play with a Black drum in the sun. If it works out half Decent, I might even build an L shaped box to put it in with a perspex window to try and concentrate the heat and insulate it a little. :0) |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
https://apricus.com.au/wp-content/uploads/2016/09/Fact-Sheet-Apricus-Evacuated-Tubes-v-Flat-Plates.pdf we used to buy tubes and manifolds from a guy in rural WA at about a third of the price because we didnt want to claim the energy credits, I dont understand all the red tape it avoided. dont want to know, life is too short. the thing that made it work for us was the pump controller, cheap and simple and it would retrofit solar to the old slow combustion stove HWS fittings. Bottom line is they lose less heat in the wind and cold so can output less water at a higher temp or work in colder ambient temps. as I said before they do struggle if you use a lot of water and the water source is close to freezing I'm confused, no wait... maybe I'm not... |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
>> I have 16kw of panels atm with another 5 kw to get on the roof.. You must have a lot of room on your roof, I don't put anything on roof's now, easier to ground mount on posts and no issues if mounting holes let the water in. Local council wants too much involvement if you bolt stuff on a roof in NZ.. there is virtually no 2nd hand PV, grid tie inverters etc here in NZ as there have never been any subsidies to attract people to install anything. The gubbermint here own 51% of the power generators so its not in their interest to want people to stop using power... >> Is the DC MPPT converter the one you did a couple of Vids on? No videos, I have a mppt tracking capacitor discharge 250 vdc to 50hz 230 ac converter design. >> Next Summer I might have a play with a Black drum in the sun.. Yeah, called a Batch water heater, they do work. Cheers Mike |
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