Solar energy Incentive

[rjj04]

I did a comparison between solar thermal hot water and using solar PV for hot water. The conclusion I came to was that, with the massive drop in PV prices, it was better to buy extra PV (panel/inverter). The kicker for me was that we don't use a lot of hot water, in terms of total volume. In the summer we don't need much at all, in the winter we kick up the power for the electric hot water heater for the shower. If you have PV, you can use the PV for A/C during the summer, when you don't need so much hot water, and for the electric hot water heater during the winter, when you don't need the A/C. Let's face it, this time of year the water temperature out of a tank on your roof will probably suffice for a shower.

70,000 for a solar hot water heater system is getting up near the 85,000 for a 3KW grid-tie PV system (less racking and wiring). Perhaps if you are a big user of hot water... for laundry, dish washing, swimming pool, hot bath, etc... then probably the solar thermal hot water makes sense. My better half seems to have zero interest in using hot water for cleaning dishes, something I always thought was useful when I "used to" do dishes

LPG is certainly a good option, once again, if you use a lot of hot water throughout the house.

Just my thoughts.

[glalt]

I'm looking at a "conversion kit".
Uses solar tubes which have some advantages.
Connects into an existing mains pressure (about 40psi) hot water system.
There are other systems also.............about $1600.00 here in Aus.(48,000 Baht)
Maybe something similar you can get there in Thailand.

http://www.solaroz.com.au/solarhotwater_products.html

Thanks for the information. I'm in no hurry for sure but I am going to look for an LPG tank type heater. That way I have the option to add a solar collector and the small circulation pump. It depends on how much LPG that unit will use. I have never had a tank type heater here but those electric units available in the USA are very well insulated will keep the water hot for several days.

The electric company in Ohio used to give you a free electric heater if you agreed to let them install a little radio unit that shut off the power to the heater during peak electric usage. Naturally I went for that deal and I would never have known that radio device was installed.

[bluejets]

Any LPG units I ever seen seem to pump a hell-of-a-lota hot air out the top.
Personally I could never see where the efficiency they claim comes from.
Maybe if the cost of gas versus electric per unit of heat energy was extremely low then some comparison of cost could be used. Other than that I'm at a loss to see it.

http://www.ebay.com.au/itm/like/4006659 ... e&lpid=107

[glalt]

I'm not sure that I could trust the LPG shower units. I could put a tank type right outside the bath room wall and feel safer. The goal is to eliminate any electrical device that needs a lot of electricity.

[glalt]

In order to take full advantage of what power my solar panels produce, I have ordered a small grid tie inverter for the house. I will install it with a double pole double throw switch. When I am away from home the switch will put all the energy into the grid. When I am home, I will still run my computer room off the battery bank. When the battery bank is fully charged, I will move the switch back to feed the grid. I paid a premium for the inverter because it is the most efficient one I found at 92 percent.

http://www.aliexpress.com/item/500W-sol ... 56486.html

[Aardvark]

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[rjj04]

In order to take full advantage of what power my solar panels produce, I have ordered a small grid tie inverter for the house. I will install it with a double pole double throw switch. When I am away from home the switch will put all the energy into the grid. When I am home, I will still run my computer room off the battery bank. When the battery bank is fully charged, I will move the switch back to feed the grid. I paid a premium for the inverter because it is the most efficient one I found at 92 percent.

http://www.aliexpress.com/item/500W-sol ... 56486.html

I haven't seen anything about that inverter. Please give us an update when you get it and hook it up. Hopefully it doesn't have any minimum Voc problems like one of the inverters I bought (KaiDeng).

Sounds like your system will start to look like my system. When you are away from home, you will put the solar panel on the GTI. If you are gone for a few days or more, how will you top up your batteries? An AC charger on a timer like I am doing?

[glalt]

These deep cycle sealed batteries lose their charge VERY slowly. I don't think it will be a problem. If they should need a charge, I do have an automatic charger that works very well with stepped charging. I'll be going down to Jomtien early next month for ten days or longer and will find out for sure how much charge they lose.

[rjj04]

Actually that inverter looks more like a relabled SUN 500G

http://www.ebay.com/itm/500w-grid-tie-i ... 3a7835c9b6

which, according to the CE certificate, is a relabled KaiDeng. A different model than the KD I have though. A lot of folks in the USA have those. A few videos on how to debug and repair them on youtube.

[glalt]

I suspect that many of the inverters actually come out of the same Chinese factory. They put whatever label on them that they want. One thing that got my attention was the inverter weight is supposed to be 4 KG. That's about double what the others weigh. When I get that inverter the first thing I do will be to verify the weight. Emails to the company I bought it from promised that the efficiency was 92 percent. That will be checked carefully also. I'll let you know what I find.

[glalt]

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[rjj04]

The case looks identical (except for the label of course), the spec is identical, and it looks as if the alibaba seller
cut-n-paste the description from the Sun/KD etc ebay sellers description... therefore I "assumed". Anyway, no matter.
Just that it might be easier if it was a Sun, as a lot of info, and parts, available to fix them. All of these small GTI inverters will fail over the next few years. Three years, five, seven, who knows... but they all will fail at some point.

[glalt]

I normally used a 600 watt inverter for the home system. When it is hot in the house, the fan comes on and it is loud enough to be irritating. I have swapped it with the 2,600 watt that I have for a spare. That one has two fans and they are very quiet. They run almost as much but they are very quiet, I'm going to keep using that one. Maybe the cheap inverters fail because people are expecting too much from them and run them near their full capacity. My inverters are all at least two or three times oversize. I have no idea what that will do for the life of the inverters but it can't hurt. According to my DC ammeter, the difference in efficiency is hardly noticeable.

[glalt]

Yesterday I received my 500 watt grid tie inverter. It does indeed weigh 4 KG. I'm of the opinion that a heavier inverter means better quality. Maybe more copper?

I hooked it up today and my cheap measuring equipment says it is .885 percent efficient. I have a Fluke meter on order and it will probably be more accurate. It will measure DC and AC current as well as voltages. My cheap meter cannot measure DC current. The efficiency is much better than the reviews that I read about cheap non-MPPT inverters.

I am re-typing this post because the electric went off again today. It was off several hours yesterday. I just dug out my old UPS and hooked it up to give me a little protection. I don't like having the computer on the grid but since the computer has seen better days, if it fries, I will have an excuse to buy a new one.

The inverter does indeed shut down when the main power goes off. Rather than the flashing green lights, the red light comes on. I'm still waiting on the double pole double throw switch so I can change from the grid tie to the batteries with the switch. My electric meter does indeed run backwards, so it is compatible with the grid tie inverter.

[bluejets]

Not quite sure what you are trying to achieve with your double pole changeover switch that you mention.

Grid systems are designed to shut down completely with loss of grid supply.
This is an absolutely necessary safety aspect of the design as you might imagine. If the supply authority decide to isolate a section of the grid, the last thing they will want is some solar powered system back-feeding the grid.

If you are having thoughts of charging batteries straight off the panels, it would be advisable to look into this a bit more.
Panel systems are inherently high open circuit voltage and in switching this DC, (which is normally illegal in many countries) you could induce rather large switching and/or fault currents.

Not to mention the switch required for this type of application(even if it was legal) is not your normal everyday run-of-the-mill changeover switch.

These things you are playing with here tend to have the potential to cause severe injuries.

Take care.....

[glalt]

The solar panels are connected to middle connectors of the double throw switch. The DC voltage can go to the grid tie inverter in one position and to the solar charge controller in the other position. This allows me to run on the batteries until they are fully charged and then to the grid tie to prevent losing energy because of the fully charged batteries. It's actually a stand alone off grid system AND a grid tie system. The grid tie inverter definitely shuts down when the main power goes off or when the switch position is changed.

At this point without the double throw switch, I have to connect the wires manually to the charge controller OR the grid tie inverter. That's a pain and using a switch is much easier. I use the same kind of double throw switch for my generator. No way can the generator power ever go to the grid. Even my wife can't screw it up.

My last post has a typo. The inverter efficiency should read 88.5 percent rather than .885 percent.

[glalt]

Here is the total dual system with the double throw switch installed. I am now normally using the grid tie inverter but when it looks like a thunder storm approaching, I move the new switch to the battery charge position. No need to swap wires now. I charge the batteries when necessary and use them during a power outage or when a storm is threatening. Everything is working great..

[bluejets]

My God.....!!!
Hope you have a 6' fence around that thing..... [-o<

[glalt]

Why? It's all DC except from the grid tie to the mains, and the other inverter to the outlet plugs.

[rjj04]

Not quite sure what you are trying to achieve with your double pole changeover switch that you mention.

Using the DPDT switch to move the power between the grid-tie inverter and the solar charge controller is what I have been doing for the last eight months or so. Works great, with on caveat.

Panel systems are inherently high open circuit voltage and in switching this DC, (which is normally illegal in many countries) you could induce rather large switching and/or fault currents.

I believe you are thinking about larger solar arrays. With say six panels in series you will get closer to 300Vdc. Glalt, if I am not mistaken, has two panels in parallel. They are at about 46V open circuit. It doesn't seem to be a problem for my system to switch to an fro.

One thing glalt, make sure you do not make the mistake I made. If you have a disconnect between the solar charge controller and your batteries, do not switch the solar panels over to the charge controller when the charge controller is not connected to the batteries... or alternatively, disconnect the batteries from the CC before disconnecting the solar panel from the CC. You may fry your CC, as I did with my little $12 CC

glalt - pls keep us posted on that GTI performance. I am most interested to see if if it drops off-line at all in the transition between sun and a cloud going over. A lot of the cheaper ones do that, so you will lose a bit of performance. At least mine have that issue.