IMHO

Talking also about lamborghini who was in indonesian hands before. Now indonesia developped an electrical car with a reasonable sportslook. Ofcourse this car can be charged by pv panels @naam

http://www.retailnews.id/car-industry-interested-in-developing-indonesian-electric-car/

I imagine Bugatti's lawyers are watching that car with interest

IMHO. The model I use isn't a like woodpecker. If I drain the solar plate then refill, the air just rushes out till the device is full then a few drops hit the roof.

Sorry, I should clarify - when hot water hasn't been used for a couple of weeks already (as is sometimes the case with my guest house system), gas pressure builds up and gets released by the valve - that's when it sounds like a woodpecker

Lorentz make some PV-direct powered pool pumps - no mains, no batteries required: https://www.lorentz.de/en/applications/responsible-leisure.html

Unlike that floating toy in the YT video posted earlier, these will turn over your pool water at normal rates so it has a chance of actually staying clean

There are some problems though... Last time I asked, the smaller pump was still well over 100K Baht (not inc. PV - i.e. 8-10x the price of a regular pump), and these are also really only useful in pools where you're manually dosing chlorine. If using a chlorinator and/or UV irradiation they still need to be powered by some other means, and you'd need to work out how to make their runtimes sync with the highly variable runtime of the pump.

both, the toy George presented and the direct PV-powered pump, are nothing but ridiculous jokes. one can't do the job, the other one is for people who like to throw money out of the window.

Yep. For less than the cost of the Lorentz pump& MPPT controller, you could buy the batteries, accessories and inverter+charger needed to make a pump and a chlorinator completely off-grid. You'd spend a little more in PV to support the longer pump runtime needed for chlorination, and the chlorinator itself - but even then, the total cost of an off-grid solar power supply would still be close to just the Lorentz pump + the PV panels it needs.

Jing Joe. There's millions of the things here.

https://www.google.co.th/search?q=air+vent+valve+for+solar+water+heater&espv=2&biw=1920&bih=965&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwj5gJqx1L3LAhWSco4KHaw1DbEQsAQIOg

I brought one with me from UK. Sorry I didn't know you were looking for one.

Lurkio. How do you make a check valve do that job?

George. In the UK the Electricity co. pay's you for any excess power you produce. This is the feed in tariff and usually you can get your installation costs back within five years. It is purely a solar thing so you would have a grid tie inverter and no batteries. There is occasionally talk of this happening in Thailand but since the electricity company belongs to the govt. and they are making money from it, it is unlikely that such a scheme will become law. What about Indonesia?

These must be available in Thailand - both of my (Thai) solar hot water systems have them... They sound like a woodpecker when operating.

Lorentz make some PV-direct powered pool pumps - no mains, no batteries required: https://www.lorentz.de/en/applications/responsible-leisure.html

Unlike that floating toy in the YT video posted earlier, these will turn over your pool water at normal rates so it has a chance of actually staying clean

There are some problems though... Last time I asked, the smaller pump was still well over 100K Baht (not inc. PV - i.e. 8-10x the price of a regular pump), and these are also really only useful in pools where you're manually dosing chlorine. If using a chlorinator and/or UV irradiation they still need to be powered by some other means, and you'd need to work out how to make their runtimes sync with the highly variable runtime of the pump.

Someone did compare ac and dc of the same size (140ltr)

My target temperature for inside the fridges was 5 degrees Celsius (second bottom shelf), this was adjusted and set during the 24 hours run up time prior to the test period for each fridge.

The room temperature ranged from 26-29 deg throughout the test (air-conditioned).

The results:

Current consumed during the 24 hour test period.

LG 240 volt fridge.99.6Ah TOTAL, with a 7Amp average whilst in the 'on' cycle and 42.2Amp peak on start up.

WAECO 12 volt fridge..42.2Ah TOTAL, with a 4.5Amp average whilst in the 'on' cycle.

http://www.fridge-and-solar.net/fridgetest1.htm

Its obvious that if you use solar panels the 12v compressor types are most suitable fridges to use.

That test is just not scientific enough - was the LG fridge an old thing from the 90's? What was his inverter efficiency? Was the inverter output waveform or frequency so bad it resulted in wasted energy? How do they perform when putting an identical hot mass inside to cool down?

The fact is there's no general answer on what's more efficient. There can be a huge variance in energy performance in fridges of the exact same size. The only generalization I think is possible is that seeing as 12DVC fridges are so rare / such a small market, it's highly likely the AC powered ones get a lot more R&D put into them.

Have a look around this website and you'll see what I mean:

http://labelno5.opr.egat.co.th/appdata/labelno5/en

One day we might have inverter fridges and freezers............Now, there's an idea for a startup.

Errm, not sure if that was a joke, but there are plenty of them already that doesn't mean they current-limit startup though - just that they run the compressor at a variable speed once started. Ditto for inverter air con, inverter pumps and inverter washing machines.

Till now i did not know that there are also 12volt fridge/freezers which look like the ac models. According to the description they consume 45-65watt depending on the model.

Im wondering if such 12volt compressor fridges also need a higher wattage as they start???

Pitty that i cant find such 12v models in the city where i am now. Camping model compressor and peltier models easy to get here.

The answer is: depends

If a 12VDC motor is just hooked directly up to 12VDC, yes - it still has a higher startup draw than what it needs to run. However, low wattage motors might also have a speed controller, which can negate the startup current demand by doing a programmed 'soft start'. Think radio controlled cars..

Would a 12VDC fridge have such sophisticated electronics though? Unlikely, given that fridges normally need to run 24/7, so are not candidates for pure PV-only power - i.e. the designer would assume there's battery power available, and that it could handle the startup demand - especially given that such fridges probably take several hours to reach target temperature inside.

Here is a vid of 3 and 5 watt led bulbs. Pitty i could not find an example of a 12volt led tube of 3watts which i myself use for my toilet. If i have time i will make a vid of it.

https://m.youtube.com/watch?v=YUXfWSxDUvc

If you're happy with it, good for you I guess

I have a collection of 3W corn bulbs sitting in a box - they are the ones I started with in various places around my house, but they have all now been upgraded so I could achieve 'normal' light levels. I'm just not ready to make the compromise to have a low-power house

Above i wrote that the 12volt lamps are in addition or supplementary to his grid lighting which he can use permanently. When there is a power outage its then not dark during his "stinky stinky" in the toilet with 3 watt led bulb.

Here is a vid of 3 and 5 watt led bulbs. Pitty i could not find an example of a 12volt led tube of 3watts which i myself use for my toilet. If i have time i will make a vid of it.

https://m.youtube.com/watch?v=YUXfWSxDUvc

Oh, these are emergency lights? If so, why the expense of solar?

Just buy some of these, and relocate the lamps to where you want them

Did i give him a good advice or not?

He said its irritating when there's an outage. He wants to ADD to his grid lighting solar powered leds to his toilet/bathroom, 1 bedroom and his living room.

I advised him to buy a cheap 20wp system with 7ah battery. In thailand it will cost roughly not yet 2000bht, incl battery.

Average use per day

3watt led x 2 hours bedroom = 6wh

3watt led x 1 hour bathroom = 3wh

5watt led x 6 hours liv room = 30wh

Total 39 watt hours.

20wp panel x 5 hours per day = 100watts. Loss 50% = 50wh

What the panel produces can easily be stored in a 7ah deep cycle battery enough for his average daily use.

So, for the total cost equivalent to some ladydrinks and perhaps also a barfine he can enjoy 3 lights for many years hahahahaha......

Did i advice him well??

Most 3W LED's are only going to make 240-300 lumens, which really isn't much light... Even my small guest bathroom (2m x 2.5M) has 18W of LED panel lights, and it feels a little dim in there. Low wattage/lumens works well outdoors in the garden, and around the house, but inside people generally want more brightness.

I just can't see 3W on the bathroom producing the desired result. 6W in the bedroom, assuming it's standard 4-5M square is probably under-done too - my guess is you'll want to double that.

Assuming it's not a huge living room, 30W of LED there could be OK though.

Again a question.

If i buy 2 batteries usually they are not 100% fully charged. Do i have to charge 1 by 1 before connect to paralel or can i connect then charge???

Just connect them in parallel - they will equalize. In fact, they don't even need to be connected to a charger for that to happen..

We have been talking about the possibility to measure voltage. if the PV panel give a certain voltage activate or cut.

Im not an electrician but is this perhaps a solution???

PV Panels output a wide range of voltage and current depending on how much solar radiation they're exposed to - the solution to getting the maximum out of them under all conditions are MPPT chargers/inverters. The solution to your startup problems are supplementary power. The solution to when to start/stop the load (i.e. when there's enough power being harvested) is going to be a highly programmable combination charger+inverter (good ones show you exactly how much PV energy is being harvested in real-time... so they know).... or just some simple math based on desired runtime and load, as already presented.

Cause I did not plan well there is a small problem if I buy other (bigger) panels.

Only solar panels of exact or similar current should be wired together in series. When you connect a 3A panel to a 3.5A panel, the overall current will be dragged down to 3A. Such a reduction in current will by all means lead to a reduction in power output and therefore loss in system performance.

http://solarpanelsvenue.com/mixing-solar-panels/

It means that I must have seperate independent systems.....or does someone know a solution to make it one (bigger) system??

You will just need separate solar chargers for each PV array, or buy an inverter+charger with dual/triple MPPT PV inputs. Don't mix different panels in an array, even following that link's guidance. The current panel variance of -0/+5% is already enough to contribute an average loss of 10%+ in a multi panel array - if you start mixing panels the losses will be great - even of they're not that far away in spec.

Consider this: an MPPT charger will extract up to 30% more power out of an array than a PWM charger. Start mixing panels and the losses will be great, because MPPT simply cannot get the optimum out of mixed cells. Anyone that thinks the losses are minimal when mixing panels must be using PWM, in which case they don't know how much power they're missing, mixed panels or not

In short, as a minimum spec for this system you'd probably use 2x 300W panels (~2400Wh/day avg min). a 200Ah 12V battery (2400Wh = ~40% DOD), and a 1000w nominal inverter that supports a 2000W peak to handle motor startup.

Thank you very much. Im orientating now on buying batteries. According to one supplier here a tubular deep cycle is one of the best for such purposes but rather expensive. He quoted a price of about 11.000 baht for 150ah. Anyone use tubular?? Other deep cycles are just a little bit more expensive than amorn in thailand.

Im planning to maintain my current system for lighting and fans. For the planned wok cooking and perhaps thay aircon i soon will buy more panels, battery and ofcourse a controller with enough amps for the future. I posted two examples videos above and if can achieve that + wok cooking i am satisfied

Got a cyclic life (DOD vs Cycles vs degradation) chart? Only that can tell you if they are expensive for a reason or not.

i.e. like this:

Which is for the Globatt Inva batteries, that are widely available/cheap in Thailand.

Just a an aside, this site is the *best* PV calculator I've been able to find:

http://pvwatts.nrel.gov/

This not only takes into account your geographical location and PV angle - it also marries that up with actual weather data, and allows you to specify the array azimuth precisely (not many roofs are exactly due South, for example). It also gives you separate numbers for DC harvest, and AC output (the latter based on grid-tie inverter efficiencies though).

Make sure you read and understand all the inputs fully, and also make sure you download the monthly/hourly CSV files, which contain much more insights that what's displayed on page.

Super tool!

All isn't lost, if using a hybrid inverter/charger that all allows you to choose priority like the MPP Solar ones.

In the case of the 260W AC unit, what George needs to do is decide how many hours/day he wants AC to operate.

From there, work out the minimum average PV harvest, and how much AC runtime needs to be supplemented by battery.

Then it's just a case of working out how much total PV is needed to keep the batteries charged, and run the load itself.

This is exactly what I'm doing, but I have the benefit of a very stable, very known, load and runtime. AC usage will be more dynamic than my pool pumps. Even so, if you work on some 'worst case' numbers, it's not that hard.

e.g.

Let's say George wants to run the 260W AC for 6 hours/day

Let's say that at least 4 of those hours are in peak PV harvesting time, so won't draw on battery other than at startup. That means the other 2 hours need to be supported by batteries.

Based on this:

Battery load is 2x260W = 520Wh. Add 15% for inverter loss = 598Wh. From there, just decide on what DOD you're happy with to size the bank...

A good solar battery will give you over 4500 cycles at 20% DOD - for that you'll need 2990Wh. At 40% DOD you'll get at least 3000 cycles, which would need 1995Wh, as examples.

To calculate PV load, we work two numbers:

Battery charge requirements: 598W/day + 20% to cover charging loss = 718W/day

Direct PV supported load = 4x260w = 1040 + 15% to cover inverter loss = 1196W/day

So total PV harvesting needed = 1196W + 718W = 1914W, adding 15% for system losses (wiring losses, dirty panels etc) = 2200w you need PV to harvest.

Assuming South facing panels at a reasonable angle (15 degrees +/-10 degrees) the worst harvesting month will be August, where you get about 4 hours harvesting/day on average. So therefore, 2200W / 4 hours = 550Wh of PV needed.

Of course, that's all based on averages though, and not every day is average. In order to give yourself some headroom for cloudy days, and cover cell degradation, you will want to increase your PV. You'll also want to include some general headroom everywhere as well too. This post is complex enough already though

In short, as a minimum spec for this system you'd probably use 2x 300W panels (~2400Wh/day avg min). a 200Ah 12V battery (2400Wh = ~40% DOD), and a 1000w nominal inverter that supports a 2000W peak to handle motor startup.

Don't start electric motors directly off PV only - work out a system using supplementary mains or batteries to assist with startup.

ok...understand.

With a timer wont work also when its cloudy and the panels dont give enough voltage/watts/amps It will drain the battery. Is there a tool which works like a switch depending on the amps? Like a thermoswitch depending on the temperature but then depending on the amps.

That's the burning question

I hybrid inverter/charger that's programmable enough could possibly do the job, but it's going to have to be clever enough that you can program it to:

1. Only turn on the 220V output when there's enough PV harvested to support the load (outside of that, use PV to charge the batteries).

2. Only use the batteries to assist with initial startup, then put them back into 'float charge' mode.

3. Turn off the 220V output when there's no longer enough PV to support the load (and not pull from batteries otherwise there's no startup capacity tomorrow).

I've read a lot of inverter manuals (but not them all) and I've not yet seen one that can be that programmable....

Also note that I have a keen interest in this, because the thing I really want to run off PV and off-grid is my pool - which has 3 motors to start, plus a chlorinator, and has runtime hours that can be supported directly by PV, and runtime hours that need to be battery supplied. I've taken my research all the way to the PV azimuth level, and determined that an array split East/West facing will mean I need less battery than the same PV panels facing South, for example

i.e. in my location, an East/West facing array results in a minimum average harvesting time of about 5.5 hours/day, vs a minimum average of 4 hours/day for a South facing array. That extra 1.5 hours of daily harvesting time makes a big difference on battery capacity required, but comes at the expense of sacrificing about 9.4% annual overall PV output.

You could probably use the hybrid inverter I linked to earlier with a minimal battery to provide the extra oomph to start the A/C.

Can the inverter be programmed in such a way that it won't run down the batteries when PV harvesting drops though?

I am using a hybrid system for precisely the reasons Crossy lists. I got mine direct from MPP Inc. Taiwan http://www.mppsolar.com/v3/

I have three PIP-MS 4Kw units paralleled up (stacked) which came to a total of US$2275 and that included the parallel kit and UPS carriage.

After sales service is excellent. Best location for the inverters is outside the house because with three units the fan noise can be a bit distracting (I think that would apply to all inverter/chargers). I did have one problem with a unit which turned out to be caused by a lizard getting into the thing, but the support I got from MPP was very good and fast.

I have been looking at the MPP inverters for some time now.. good to hear some actual feedback from an owner.

Here are some examples of pv panels directly connected to an inverter. I have no grid connection. Till now my house is 12volt house.

https://m.youtube.com/results?q=solar+panel+dirext+to+inverter+no+battery

I only watched the first one, where a guy was using a 50W PV with 20VDC open circuit voltage.

This only works because under this exact load, the panel outputs a voltage within range of what the inverter actually wants - any more or less PV voltage and it just doesn't work anymore. On top of that, this inverter will not exhibit an ideal load on the panel, so he's never getting the full 50w out of it, no matter what he does. His 20w CFL load is probably about all it's good to run.

The thing about PV is, the actual range of voltage it outputs varies wildly based on solar energy it's exposed to, the the load that's placed on it. it's not like a battery where the voltage range is minimal.

Lets assume he is right, how many wp solar panels must be used to run that 260watt ac and is a 500watt inverter enough??

What you need to start a 260w AC isn't easy to calculate without understanding it's start-up requirements. AC's have three main motors: 1) the inside fan motor, 2) the compressor, 3) the outside fan. The fans are usually only a small % of the overall power draw. For a 260w unit, I'd assume maybe 40-60W a piece for the fans.

Usually, the inside fan blower start before the compressor, which might start before the outside fan, or they might start in unison - so we have 2-3 startup stages to consider.

Assuming startup current draw is 4x nominal:

1. Inside fan: 40-60W with a startup current of 160-240w

2. Compressor: 140-180w, with a startup current of 520-720w

3. Outdoor fan: 40-60W with a startup current of 160-240w

or:

1. Inside fan: 40-60W with a startup current of 160-240w

2. Compressor and outdoor fan: 200w-220w with a startup current of 800-880w

Double these numbers for worst case (8x) startup current if you can't get actual real specs.

So that means, you need an inverter with a peak ability of either 900w (4x) or 1800w (8x) otherwise it just won't start. The same capacity is needed for the PV.

Most inverters can support around 2x their rated current for short-term peaks.

It seems a terrible waste of PV to provision 4x to 8x of what you actually need, just because you want to start electric motors without a supplementary power source!

Short version:

Don't start electric motors directly off PV only - work out a system using supplementary mains or batteries to assist with startup.

@muhendis, ok...i understand.

Coming back to the favorite subject of @naam and the 260watt aircon, a question.

If all my alternative efforts to cool down during the day fail, is it possible to run that ac directly from the panels (300wp) via an inverter, thus not connecting to a controller and battery bank???

If possible, it means that the ac will run automaTicly during (hot) top peak hours and ive achived my goals. In the evening i dont need to run that ac, not even a fan is needed.

Added: Sorry double posted

I have never heard of an inverter that operates direct from PV, but is not also designed for grid-tie (i.e. they all require the grid to be connected/functioning for it to produce output).

And there's a good reason why... generally speaking it's fair to assume an electric motor draws about 4x-8x it's nominal wattage at initial startup time. So in the scenario of the "magic inverter" above, it would need to be smart enough to only switch on the output when there's sufficient excess power for startup to be successful, which also means you need to over-spec your PV 4x-8x too...

What you want can be achieved though using a conventional grid-tie inverter - but you won't get auto start/stop - it will be up to you (or a timer) to cycle the AC on/off. In this scenario, the initial startup current is supplemented by the grid so you don't need to over-spec your PV, but if you run the AC for too long it's going to draw from the grid - there's just no way to guarantee the AC runs off PV only. Also if the grid is down, so is your PV, due to anti-islanding feature all such inverters have.

Another theoretical "magic inverter" would be one that uses (small) batteries to supplement motor startup demand only. I've never seen such a device though. All off-grid inverters I know of are going to suck your battery bank dry as PV output falls each day - so there's nothing left in the batteries the next day.. That said, a timer is a potential solution to this... but again, not really automated. You'd need to monitor PV output and adjust runtime duration pretty regularly.

Permit me to ask again about batteries. Ive read about a desulfator, only about 900bht. According to the supplier you can connect it also continiously. Will it work?

FUNCTION

The High-frequency Peak Pulse delivers an electronically controlled pulse to the battery causing crystalline sulfates to dissolve back into the electrolyte and so restoring battery function and electrolyte strength regaining the batteries ability to receive charging current and deliver discharge current.

ADVANCED TECHNOLOGY

Many desulfator products use an old technology inductor design to generate the pulse to desulfate a battery. This old technology creates a harsh inductor peak that can be damaging to the battery plates.

NEW CYCLIC PULSING FUNCTION

In a similar manner to a Pulse battery charger (charge rest charge rest etc) a cyclic desulfating pulse function (pulse rest pulse rest etc) optimizes a batteries recovery process. This method of desulfation has been implemented in the new Auto Pulse Desulfator

AUTO PULSE DESULFATOR BENEFITS:

1 Increases Battery Power

2 Extends Battery Life

3 Battery Charge Faster

4 Longer Discharge

5 Prevents Sulfate Build-up

6 Reduces Evaporation

COMPETITIVE ADVANTAGES

1. Fully Automatic voltage selection. 12V 24V 36V and 48V

2 New Cyclic pulse generation method for improved capacity recovery

3 Soft Peak Pulsing

4 Auto cutoff function to prevent over discharge of battery

5. User Configurable override for manual voltage selection:

CUTOFF VOLTAGE

Display. Cutoff voltage

12V battery C12. 11.0V

24V battery. C24. 22.0V

36V battery. C36. 33.0V

48V battery. C48. 44.0V

God quality solar chargers have this type of feature built in.... they will even work out the optimum time to do it, based on bank usage. The principle of it is pretty simple: just over-volt the cells by about 20% and you boil the junk off the plates. The only trick is when to do it, and how long to maintain the extra voltage. Like I say, good quality solar chargers manage this all for you.