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Noobie With a 'Clean Slate' That Needs Help!


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I guess the experts will have heard this a 1000 times already but as a total noobie I have to ask as I start on my solar journey.

I must start by saying I have a 'clean slate' and no house or equipment to talk of yet, but I will start in the coming month to build in the Lowveld. I have thought a little in the 'house design' as far as 'solar' was concerned but only by having allowed for 60m2 of roof @18° (garage and carports) these can face within reason in any direction I will just have to look at trees and things.

Is it best to face all panels North? or I read these perhaps should be split in different directions to get morning and afternoon sun.

Batteries and inverter will sit in the garage which will be about 6m from the main house DB.

I plan to be totally off grid.

That's it as far as planning is concerned. Certainly to start my solar quest I have a several questions that I would be grateful for an answer to please, to assist me in going forward. I really cant afford to make mistakes that will be costly for me in the long run.

So..

1. I intend to have 2 geysers. The main geyser to run off a 'Geyserwise' set up with separate PV panels and controller. Should I have a similar set up for the guest bathroom which will only be used for the occasional guest? Or should I account for this additional geyser power requirement in my batteries sizing (see question 2) with an additional geyserwise? The other option I thought, would be to go for an LPG set up for HW and forget the geysers altogether. I have a costing of around 30K for the LPG installation. Of course 30k will go a long way towards my solar costs if it would be more cost effective to be totally solar. 

The LPG of course would also give me ongoing gas costs as well. We could cook with a gas hob and remove that electrical hob element from the total watts usage to make things even smaller.  What do you guys think?

2. When I start listing down the appliances and lights, TV, computers etc.. (total watts) I am al little confused as to what I should allow for in the final figure as a 'load' requirement. As I see it I have 3 scenarios. Things we use everyday like lights and computers, fridge/freezer, TV, geysers, microwave, hob for example, then there are things we would switch on once and while like oven, dishwasher, washing machine, covered patio lighting, garage lighting so not everyday. Then we have things we would switch on only during summer/winter months like fans, humidifier, small electrical heater (2kw) or AC's. What about AC's can they run off a solar system efficiently? and for how long? Is it practical? what do you guys advise about AC's? So what should I include in my calculations to establish load for panels and battery sizing and quantity? Day usage only? Winter summer use and or occasional use? So what is my peak load?

I think I can start from there and I am sure more questions will be forth coming as I move forward

 

Regards and thanks in advance.

Limpopoboy

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In order to generate 20 kWh per day I have 4.5 kW of panels on the roof. It can do more, but I don't have anywhere to send the power after 12h00 in the day. The cost of the panels work out to be around R26k, which is just under R1300 per kWh. Thats not so bad for power in the day. It is cheap enough to add as many panels as I need to power all our appliances during the day. 

My Dyness battery bank is worth R36k for the usable capacity of 5.8 kWh, lets say 6 kWh for convenience. This works out to R6k per kWh or roughly 4.5 times the cost per kWh for solar in the day (excluding the generation cost). Including the generation cost as well it works out to almost R14k per kWh at night. So this makes night time power more than 10 times as expensive as day time power. This is way more expensive than the gas that you will buy to power a stove and perhaps even a geyser. We have not considered the cost of replacing the batteries in 10 years in this calculation.

So unless you have a ton of money to drop on batteries, forget about powering an electric stove and oven combination. It can be done, but it is expensive, unless of course you can convince your wife to cook only over lunch time on sunny days. We're in the process of replacing the electric stove in the cottage with a gas stove and oven combination. The electric geyser is on a timer and runs only during the day time hours. However, keep in mind, even with a geyserwise, if you have a cloudy or rainy day, you don't have a lot power, if any, to waste. Or put another way, if the sun is too weak to heat up the water on the solar heater, the sun is likely to weak to power the heater element, and you'll be showering in cold water.

Although gas is expensive I believe it is still way cheaper than night time power from the batteries and I would heat with a gas heater , or better yet, a fireplace, and cooking would be done on only gas (with an electric hot plate as backup) and heating with a gas geyser. This is what I prefer and use in the main house, and I think this is a nice compromise. 

 

Perhaps the guys that have been on solar for a while will have a better perspective.

 

To answer your question about the AC. My AC uses 950W when the compressor is running. This is not a problem for the solar during the day. Once again, as with the stove, running the AC at night is a very expensive prospect. I still want to experiment with cooling the room during the day with solar, and then keeping it cool at night running off batteries. It looks like the duty cycle is low enough once it has reached temperature that it might be viable to run it at night. However, I will need to double my capacity to cater for this as we don't make it through the night on batteries yet.

Edited by Paul Greeff
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2 hours ago, Paul Greeff said:

 

So unless you have a ton of money to drop on batteries, forget about powering an electric stove and oven combination. It can be done, but it is expensive, unless of course you can convince your wife to cook only over lunch time on sunny days. 

Some hobs is available with a combination of gas and electric. When solar is available we use solar.  

 

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A year ago I built my first house and my first solar system which is off-grid.

I'm writing this also for my own reference so don't be offended if it's all said before or if the post is too long.

Just some thoughts:

Keep it simple! (As simple as possible, but not simpler 🙂).

Start with a big inverter and solar charger for future proofing. Be sure to have monitoring of state of charge, solar production and AC consumption with graphs.

Start with the bare minimum of solar panels and battery capacity. For a new install, Lithium and 48 V is nearly mandatory. Make sure that on your roof, more modules can be installed easily without moving the existing ones.

After having moved in, learn your usage patterns. See if you can adapt your usage to what's available during day and night. 

If you can not adapt, add modules and batteries as needed.

Increase solar production until you get 100% state of charge before sunset most of the time. (Depending on weather patterns).

Increase battery capacity until you get a comfortable, not too low SOC (state of charge) before sunrise most of the time

Long term high power loads at night are the most difficult. AC or heating. Every degree less of AC or heating for a full night makes a big difference. Use as little cooling or heating as you can bear, then determine the kWh needed and add battery capacity as long as it makes sense.

The cost of battery power per kWh is important but it must be related to the cost of the whole house. If you have a luxurious or large house, it does not matter if you spend a 20'000-40'000 ZAR on more batteries. 

I would hate to juggle gas bottles for the rest of my life.

If still designing the floorplan, put your sleeping room on the shady side in the afternoon. Rooms in the same house can vary a lot in night time temperature.

Find out if you can build a cooler roof than standard.

I distinguish 4 kinds of loads:

Low power, short duration: TV, music. Irrelevant.

Low power, long duration or always on: Alarm, cameras and NVR, phone and notebook chargers. Base load. 

High Power, short duration: Microwave, electric kettle, bread making machine, toaster, electric pressure cooker, induction counter-top hot plate, washing machine, hair drier. Stick welder. The electric kettle, electric pressure cooker, microwave and induction hot-plate are extremely efficient. See if you can move some of these into solar production hours.

High power, long duration: AC or heating. Comfort vs. battery cost. 

If I had solar panels for geysers, I would surely make them switchable to the main system. If your water is fully hot by noon or sooner, might as well use that solar production elsewhere.

I can't imagine two different orientations for the panels to be more good than bad.

Simplicity means quality of life. AC or heating means quality of life. Both can be a luxury worth money.

The garage is only semi-secure. Normal garage doors are easy to pry open. Burglars will steal your entire solar system if nothing stops them. It would be not trivial to come up with a secure garage door.

Consider security and fire hazards in your planning.

Personally, I would not enjoy having three separate solar systems (two geysers and the house).

What I did:

- I bought expensive Victron inverter and solar charger because I hoped for above average reliability and durability. I wish I knew which of the less expensive brands are also good and reliable.

- I bought a high power inverter because I wanted the ability to stick-weld.

- I bought the bare minimum of 6x 300 Watt panels because we have extremely reliable sunshine in desert Namibia. That turned out to be more than enough. A local solar salesman wanted to sell me 18 panels, lol.

- Bought 7 kWh of Pylontech batteries because I thought 5 kWh Lithium to be the bare minimum and the next size modules were not much more expensive.

- Without any special projects, I get average of 50% state of charge each night. Lowest I ever had was 10% after two exceptionally dark days.

- I get 11 kWh of solar production daily, half of it unused most days.

- I run heaters in the cold season, but for now only during solar production and only for one room on modest power.

- I'm going to add another battery (total of three Pylontech, 10.5 kWh) to have modest heating power all night and to have very shallow charge cycles when not heating.

- My solar equipment is in a semi-strong-room along with the camera NVR and alarm system plus two safes for documents and pistol. Burglars should not be able to snatch the NVR easily. The top of the room has steel mesh. I built my own strong doors of steel with the help of a welder. Our local neighborhood watch reports fairly frequent burglaries but fortunately (almost) no home intrusions with people inside and assaults. The strong room provides some fire-separation.

- My cooking and washing just don't make a serious dent in battery capacity. But I make simple meals and I have efficient appliances.

- I don't run a fridge and having no TV is great.

- My house is exactly rectangular and includes the garage. Trespassers can not sneak up without being captured by four cameras and they can not hide behind anything.

- My bakkie including touring equipment cost more than the house.

- I aligned the house exactly east-west for the solar panels. I specified a steeper roof than normal, 25%, exactly north facing for better production during the winter. This was silly though because the difference is small and solar panels are cheap.

- My geyser is working with a 2 square meter water solar collector but I regret that. It took me three attempts to get the piping right myself (plumber was an idiot). I should have used a normal geyser and more solar panels that I can switch over between water heating or battery charging. It's working fine now though. 

- A geyser placed closely to the kitchen and bath will give much quicker hot water.

Question:

How many kWh does a stove and oven combo consume for a big cooking event? With my simple cooking, I just don't consume much at all.

 

Edited by rectangularBuilding
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Thanks for quick reply, that's motivating.

About cooking, be sure that it really takes those giant kWh values for a big meal. These hot plates have high peak consumption but they cycle on and off, same with the oven. But I would agree that hot plates (not inductive) and solar are not the best match.

Hot water depends a lot on local weather and if the users accept the occasional waiting for the shower. If they don't, they're spoiled brats 🙂.

In my super sunny region, I have a giant surplus of hot water for one person and plenty for two person having long showers.

Look, I'm running a mini kettle, toaster, and a mini pressure cooker in my touring bakkie every day and I could easily run a microwave if I had space. I'm also running a heating blanket on the lowest setting all night long. But I'm not claiming that this stuff is cheap to do.

I'm usually not posting on forums a lot at all so I'm not sure what possessed me this time. But don't let that bother you. Best regards.

 

 

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@Limpopoboy totally solar is not easily doable unless you're willing to timeshift some things, to daylight hours and still potentially go overboard on the battery side. We use LPG for cooking, no real oven at the moment. As for hot water, you can always do a solar unit with maybe a switchable donkey as a backup, using PV to generate electricity to heat a HWC, is very inefficient, I think, someone can maybe come up with the sums on this, we've got a 12 evacuated glass tube HWC with 100 or 150l tank and so far, so good, but have not really had a full winter with this thing, showering at around sunset would in winter provide warm enough water, but it seemed by 9 or 10PM it probably wasn't really usable anymore, but I'm not 100% certain, being gravity fed and having probably a 30+m pipe to the shower could also mean I gave up too early the 2 or 3 times I tried it at night, last winter, possibly, it seems its around 5 minutes or so, before the warm water has pushed out the cold and reached the bathroom.

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I had my geyser wall mounted (outside) opposite the bathroom and it took five seconds for the hot water to arrive in the shower. Wall mounting keeps the geyser warmer because there is less wind. I could hot shower all night long and had usually lukewarm to pleasant water in the morning, depending on previous day usage and night temperature.

Wall mounted geyser means you either need a circulating pump for a solar collector on the roof or you use PV power to heat. I had a circulating pump hoked up to a tiny 15 Watt panel but the constant hum of the pump at various pitches drove me crazy. This sound goes through the pipes and walls, not primarily through the air. Structure-borne sound is extremely hard to get rid of. It was the best and most expensive pump available.

I had to get rid of the whining pump so I moved the geyser from the wall onto the roof so that it is higher than the solar collector. In that case, thermosiphon effect is available and the noisy pump is unneeded. Then I installed thermal lagging onto all the pipes (PEX, and copper only near the geyser) and two, not one geyser blankets. Now I have huge amount of hot water day and night and lukewarm to pleasant water in the morning. Hot water now takes 15 seconds to arrive.

If I had photovoltaic geyser heating, which notably does not involve an inverter nor a battery, I could move the geyser back to the best spot, the outside wall.

Those PV geyser kits seem overpriced because you only get two or three panels but they make you buy a controller box and a MPPT box.

If I had to do it again, I would try a normal geyser and 6x PV panels in series connected directly to the standard heating element. The voltage is about right and the loss because of lack of MPPT is more than offset by money savings. Then I would make these 6 panels available to the main solar system with a switchover. But this would be experimental and is not sure to work. If it wouldn't work, I would get a solar upgrade kit for the standard geyser. Then the financial risk would be low because I needed 6 panels anyway and the standard geyser could be used.

I'd rather have 30 meters of wire than 30 meters of pipe by the way 🙂.

Edited by rectangularBuilding
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@Kalahari Meerkatthanks for the input. We currently time shift many things with our Eishcom supply (when its on)  so don't see it as a problem. I am not really a fan of solar geysers just purely on an aesthetic look if nothing else. Our hot water needs (bathroom, scullery) are only a few meters apart so no issue with water draw. I really would like to go full solar but...  I must decide soon 

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8 minutes ago, rectangularBuilding said:

I had my geyser wall mounted (outside) opposite the bathroom and it took five seconds for the hot water to arrive in the shower. Wall mounting keeps the geyser warmer because there is less wind. I could hot shower all night long and had usually lukewarm to pleasant water in the morning, depending on previous day usage and night temperature.

Wall mounted geyser means you either need a circulating pump for a solar collector on the roof or you use PV power to heat. I had a circulating pump hoked up to a tiny 15 Watt panel but the constant hum of the pump at various pitches drove me crazy. This sound goes through the pipes and walls, not primarily through the air. Structure-borne sound is extremely hard to get rid of. It was the best and most expensive pump available.

I had to get rid of the whining pump so I moved the geyser from the wall onto the roof so that it is higher than the solar collector. In that case, thermosiphon effect is available and the noisy pump is unneeded. Then I installed thermal lagging onto all the pipes (PEX, and copper only near the geyser) and two, not one geyser blankets. Now I have huge amount of hot water day and night and lukewarm to pleasant water in the morning. Hot water now takes 15 seconds to arrive.

If I had photovoltaic geyser heating, which notably does not involve an inverter nor a battery, I could move the geyser back to the best spot, the outside wall.

Those PV geyser kits seem overpriced because you only get two or three panels but they make you buy a controller box and a MPPT box.

If I had to do it again, I would try a normal geyser and 6x PV panels in series connected directly to the standard heating element. The voltage is about right and the loss because of lack of MPPT is more than offset by money savings. Then I would make these 6 panels available to the main solar system with a switchover. But this would be experimental and is not sure to work. If it wouldn't work, I would get a solar upgrade kit for the standard geyser. Then the financial risk would be low because I needed 6 panels anyway and the standard geyser could be used.

I'd rather have 30 meters of wire than 30 meters of pipe by the way 🙂.

@rectangularBuildingHave you had any experience with or know about Geyserwise set ups? This is with dedicated PV panels. When I enquired about can I switch over and add the panels to my solar array when and if needed I was told no?

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Sorry, no experience with any of the PV geyser kits. They just might use 24 V panels rather than 37 V. They might say no to dual-purpose panels because of liability and warranty. 

I can not provide a sure solution. I just mentioned an experiment that I would try.

Under the roof solar geyser is possible and can be done with thermosiphon effect. But you would worry about leaks or overflowing catch trays and access for maintenance would be hard. It would keep the geyser warm, which is good.

Edited by rectangularBuilding
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16 minutes ago, rectangularBuilding said:

Sorry, no experience with any of the PV geyser kits. They just might use 24 V panels rather than 37 V. They might say no to dual-purpose panels because of liability and warranty. 

I can not provide a sure solution. I just mentioned an experiment that I would try.

If I may.  If you have like nothing follow this route:

  1. Put led lights in where you can stick to 12V or 24V lights then you can use a small battery for load shedding
  2. FIRST convert your geysers to solar geysers the glass tube ones.  That make and immediate impact
  3. Second if you do not have a gas stove switch over.  Gas will cost you +/- R100 per month ... A gas stove you can buy and it pays off in 18 months.  Not these fancy Smeggs but a hobb and 4 / 5 plates Deffy very good ours are 10 years old still the same temp as day 1 and no maintenance requires. 
  4. Decide what you want on when Eskom is off. If you do not have geyser wise simple timer will do the same from builders for R3xx. The rest of the stuff is a gimmic.  Therefore a timer and glass tubes is very efficient and a geyser wise simply switches electricity that any fancy timer can do for a lot less.
  5. If you have swimming pool etc.  Then simple during the day a grid tie inverter with a feed back probe will stop decrementing your prepaid meter else you feed back. If you have old style meter the meter will turn back not recommended but check with Eskom I am sure you are paying them and they require a new meter and they will accept your electricity.  Might take a while to get all sorted but the smart meter system does not loose data and then L & G is highly recommended.
  6. once done calculate your Watts required for 2 - 3 hrs and then your system will cost a lot less and you do not require fancy stuff and less than 1.2 the cost of Lipe batt etc.

A system like this will cost +/- 40% of the fancy stuff and know if they want more than +/- R60K you most probably just wasting money.  This is not a fancy option but will do the trick and save money from day 1 with out sponsoring China ...

Once done kaas dit en geniet dit.

 

Edited by Erastus
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@ErastusThanks for the feedback. Our intention for sure is NOT to have an Eishkom connection. We have an empty stand and no connection currently.  The dilemma is the how we heat the hot water and cook LPG or solar. It would seem there will be enough from the PV panels during the day to give a us a tank full for showering and washing up right through the day and early evening. I suspect even with double blankets warm enough for the mornings.  As there is only two of us LPG would make sense

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17 hours ago, Limpopoboy said:

I live in the lowveld so sun is normally plentiful

Here's a map of PV power available across SA.

South-Africa_GHI_mid-size-map_156x161mm-

Note that it increases as you move NW. Upington is PV heaven. Durban and the South Coast are not as good in this regard as Johannesburg. The Lowveld isn't Durban but it isn't Johannesburg either (let alone Upington). 

The mistake I made when I bought my system and did some calculations to see if it would pay for itself is to forget that sometimes we have overcast days and all this solar stuff doesn't work so well. When the sun shines in Jo'burg it is nice and bright, but we have our gloomy days as well and right now we're in a prolonged gloomy spell.

Anyway, you might look at this data and decide that you need to get a few more panels, or, since you're building from scratch use the method suggested above whereby you allow for expansion and monitor and add until you get to a sweet spot.

Edited by Bobster
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