New to Solar

Stdyhand

First off some history. My in laws are wanting my wife and I to move to Arizona so were planning to do it. My wife wants to build one of those small tiny tumbleweed homes on a trailer to live out of that for a little while. I am going to run solar and wind power with a generator as a backup. I was planning on using a point of use hot water heater for the shower. I want to use thermal hot water for the sinks since not much hot water will be needed and it isn't as big of a deal if the temp starts dropping off. Composting toilet will be our only option until were hooked into a septic.

Back to the electric. I plan to mount the 250w panels to the roof along with two wind turbines at each corner of the roof since they should get good wind coming across the open desert. I will be using two small deep freezes, one converted to a fridge, a computer and 52" Sony Bravia LCD tv which also serves as my pc monitor. (I know its a little big for a tiny house but it mounts flat against the wall and I wasn't ready to let it go. ) I may also be powering a few lights, including a couple of outside flood lights.

For my normal home with a regular stand up fridge, 24k BTU window air unit, lights, tv, blu-ray player, etc. we normally average 1KW an hour with everything running, but of course it doesn't all run all day long.

My question is could I use more batteries for storage and less solar panels as long as I use the generator to top up the batteries each day? Eventually I plan to build a 7-10KW solar array if I can keep finding good deals on panels. Just a shot in the dark, how much power do you think I would need to run my two deep freezes, few lights, computer, 52" LCD tv, microwave, electric skillet, etc. I know it helps to know the exact wattage use for each item but I have no idea so a shot in the dark will suffice. I plan to use install more panels than I actually need anyway.

Cariboocoot

Re: New to Solar

Welcome to the forum.

Do yourself a great big favour and don't do this.

Some of the red flags I see:
24,000 btu A/C unit.
Wind turbines mounted directly to the structure.
Two deep freezers.
Microwave.
Electric skillet.
Building a 7-10 kW array based on "finding deals".

What you need is a plan. One that will work and won't be a nightmare to try and implement. Buy a Kill-A-Watt and start measuring everything you will be using for real. You need a specific Watt hours number target or else you are going to be living in "Headache City" which is just East of "Bankrupt".

You probably do not average 1kW per hour, but I'll bet you consume 24kW hours per day. That is not difficult at all. Powering it off grid is.

52" TV may pull down 200 Watts. Run it for a 2 hour movie and you've got 400 Watt hours. Refrigeration equipment typically pulls 1kW hour + per day. If the computer is a desktop it will be sucking up power like the TV. All those "few lights" add up to a lot of Watt hours in the course of a day.

Once you have a known quantity of Watt hours to supply (and a maximum Watts) you can figure out how big a battery bank you need and then how to recharge that. Buying stuff at random and hoping it works out is a gamble you do not want to take.

Remember: I spend much of my time fixing systems that do not work, and most are a result of them not being put together with a plan.

zoneblue

Re: New to Solar

Stdyhand wrote: »

I know it helps to know the exact wattage use for each item but I have no idea so a shot in the dark will suffice. I plan to use install more panels than I actually need anyway.

Solar electric is a fine balance between doing the job and not breaking the bank. There are other limiations too, roof space will likley be one of yours. So as coot says, shot in the dark will 20:80 percent end in tears.

If you dont plan on using a professional system designer, then be ready to hunker down and do some serious research and planning. it took me about a two weeks full time i kid you not, to do this for our small house.

The kill a watt is the first place to start., measure the roof, and set a budget. Then we have something to work with you on. Actually the details are the easy bit.

solar_dave

Re: New to Solar

Is your location completely without the grid?

NorthGuy

Re: New to Solar

If you have a generator and some amount of batteries, you can get through everything - clouds, rain, snow. You can size the generator so that it can run your loads and then some to charge batteries at the same time. You size your batteries to get you through between generator runs. This gives you a very reliable independent power system (and you can easily add RE sources to it).

This system (batteries + generator) is extremely expensive to run (fuel + generator amortization) and noisy, but it gives you a base. Once you have it, you can start adding solar panels. The more panels you add, the less are your generator runs. Panels are cheap and last long, so the power will get cheaper. At the beginning every additional panel will help a lot, but eventually you'll see that you have so much panels that often you do not need the energy they produce because your batteries are already fully charged. In this situation, adding new panels will be less valuable than it was in the bigginig. At some point, you'll see that it doesn't make any sense to add any more panels. That's the perfectly sized system.

Adding more batteries will not help much. Batteries are expensive and don't last long, so it is not a good idea to buy more than the necessary minimum plus some safety margin. Also, the bigger your battery bank, the more difficult it is to keep it properly charged.

Stdyhand

Re: New to Solar

Thanks for the reply. A headache is exactly what I am wanting to avoid. The items I listed are only what I'm currently using. I currently live in a very humid area, hence the reason for the A/C. I've visited family in Arizona in the middle of summer many times and it was surprisingly more comfortable due to the arid climate. The A/C may not even be needed but it certainly is here with 100% humidity. I will buy the killowatt meter today to make sure, but the items I'm currently using run for many hours a day due to the kids and I burn approximately 24 Kwh in the course of a month. That usage is what the electric company is telling me and I did verify on the meter outside also. This was taken in the middle of summer when the a/c was being ran constantly. It is much less during the winter months.

As far as space for solar panels/wind, it doesn't have to be put on the roof. We will have several acres of land and we can use a 1/2 acre for the panels if needed, mounted directly to steel poles set in concrete. There is no one around except open desert so the amount of sun and wind and space to put them is not an issue. I am not rich, but my wife and I will buy more panels/batteries etc. to install if needed. I'm figuring about 25-30 panels to power most of what we have now, but again we may not even need the A/C. I am trying to figure for worst case scenario. To the one who asked, yes it is completely off grid by many miles and that is what I like the most.

I've figured out how to calculate the number of panels and batteries, but I find the efficiency of each unit confusing. I understand more batteries is potentially more storage and less they must be drained during a day, but I'm assuming an inefficient system would require an even larger array.

Anyway, I will update this with the wattage requirements for the items I'm using and you can see what numbers you come up with.

jcheil

Re: New to Solar

If you needed to produce 24kwh per day with solar you are going to be looking at a "rough" guess of a $30k investment minimum. Just the batteries alone will be close to $16k.

Conservation is the key. I live in Florida too and the humidity sucks. So I know what you mean about the A/C being needed. And swamp coolers don't work here.

But I can tell you, with the properly designed, insulated, vented structure you would be amazed how you can be "comfortable" in Florida july/aug 95+ temps without A/C. My neighbor did exactly that, a super insulated building, tons of windows and sliding doors for cross breezes, an 8' wrap around screened porch (as a continuation of the same roof pitch as the house) and the entire structure is 8' off the ground on 8x8 posts. I was really surprised how "comfortable" it was in august when the outside temp was 95+.

And at night, a small 5000btu window unit keeps only the bedroom cool when absolutely needed. Although even to be able to run the 5000btu requires a rather large 2500w+ system or a small 1000w generator burning 1 gallon of fuel per night.

It's all about the balance.

zoneblue

Re: New to Solar

Some good answers there for sure. The thing about starting afresh is that you can start afresh. Reexamine the appliances that you use, to see if there are more efficient ones. Are there other ways to achieve the need that dont involve (large amounts of) electricity. Passive solar design noted above is a good example. New generation LED lighting, etc etc.

This approach will help leverage the dollars you spend on RE gear, make it go a lot further. Good luck and enjoy the ride!

Stdyhand

Re: New to Solar

The LED lighting is great. I was recently looking at those. My current house uses all fluorescent lighting which greatly lowered my bill over the old incandescent bulbs. I'm actually looking at LED lighting now for each time a bulb burns out, which isn't very often. I was thinking of installing recessed LED lighting. We will be staying in a smaller home so I'm certain our heating/cooling needs will be far less than they are now. We likely will start small and add what is needed.

So far I've checked my fridge, though we plan to use two deep freezes, one as a freezer and one as a fridge. I read they were better on power in the long run due to being more efficient. My current fridge however is using 120 volts, 1.82 amps (rated for 4.5 amps). It showed 127 watts being used with compressor running, but 120 volts x 1.82 amps =218 watts. Not sure which is right.

My desktop PC, 22" monitor, DVD player and camera running on one plug pulled about 263 watts average.

My 52" Sony Bravia, 2nd Desktop PC, blu-ray player, surround sound system, printer, and ISP modem all pulled a combined 580 peak watts and average of 498 watts.

I wouldn't be taking some of this stuff but for now I am going to use it for my calculations.

Cariboocoot

Re: New to Solar

Refrigerators will return various results owing to the difference in effort the compressor has to make depending on the state of the refrigerant. 127 Watts running is not unusual, but it may go up just after a defrost cycle when it has to work harder to re-compress and get the pressure balance back. Don't forget most of them have automatic defrost which typically pulls 500 Watts for a while whether you want it to or not, and disconnecting this is not such a good idea.

Interesting comparison: my satellite Internet set-up pulls 50 Watts total (not including computer). The refrigerator about 120, plus a defrost cycle or two. In a day each will consume roughly the same amount of Watt hours: 1200. This is because the Internet connection is constant while the refrigerator cycles on and off.

Stdyhand

Re: New to Solar

It has been over 13 hours and the meter shows the fridge has only used .55 kwh so if I'm reading that correctly it is 550 watts. It isn't as bad as I thought it would be. That averages out to be about 1 Killowatt a day. My tv and desktop computer is far worse than that. It wouldn't take much to power the fridge and most of the small stuff, but it would take a lot to keep the tv and pc running.

jcheil

Re: New to Solar

Stdyhand wrote: »

It has been over 13 hours and the meter shows the fridge has only used .55 kwh so if I'm reading that correctly it is 550 watts. It isn't as bad as I thought it would be. That averages out to be about 1 Killowatt a day. My tv and desktop computer is far worse than that. It wouldn't take much to power the fridge and most of the small stuff, but it would take a lot to keep the tv and pc running.

Just remember it is winter now. Summer will likely be more.
For me in Florida, my summer usage is pretty much 2x the usage of winter usage.

zoneblue

Re: New to Solar

You can do it two ways. Leave the watt meter on each appliance for 24hrs, and see what you actually use. Or measure somethng when its running and then say well use this appliance for X hours per day average. When you have all that talley it up like so

item, nhours, watts, Wh/day

sum the wh/day column, add 20% for contingency, and thats your target load.

Desert Rat

Re: New to Solar

I keep tabs on several refrigerator/freezers and chest freezers. A typical 18 cu ft. refrigerator/freezer uses 1.5 kWh/day, and that is here in the west Texas desert in the summer in a non air conditioned space with ambient high temps of 100-105 degrees F. A typical 8 cu. ft. chest freezer uses 1.2 kWh/day in the same conditions. You can get a good idea of consumption for any fridge or freezer by mulitplying the published Energy Guide number by 1.5, then divide by 365 to give the daily usage. Again, this is for summertime high temps at or above 100. Your results should be about the same in Arizona.

MikeSus

Re: New to Solar

jcheil wrote: »

If you needed to produce 24kwh per day with solar you are going to be looking at a "rough" guess of a $30k investment minimum. Just the batteries alone will be close to $16k.

Conservation is the key. I live in Florida too and the humidity sucks. So I know what you mean about the A/C being needed. And swamp coolers don't work here.

But I can tell you, with the properly designed, insulated, vented structure you would be amazed how you can be "comfortable" in Florida july/aug 95+ temps without A/C. My neighbor did exactly that, a super insulated building, tons of windows and sliding doors for cross breezes, an 8' wrap around screened porch (as a continuation of the same roof pitch as the house) and the entire structure is 8' off the ground on 8x8 posts. I was really surprised how "comfortable" it was in august when the outside temp was 95+.

And at night, a small 5000btu window unit keeps only the bedroom cool when absolutely needed. Although even to be able to run the 5000btu requires a rather large 2500w+ system or a small 1000w generator burning 1 gallon of fuel per night.

It's all about the balance.

11.31kw system generating 50kWh right now was only $28k Prices are dropping. (This is the system listed below)

PM me and I can give you my installers info.

Blackcherry04

Re: New to Solar

MikeSus wrote: »

11.31kw system generating 50kWh right now was only $28k Prices are dropping. (This is the system listed below)

PM me and I can give you my installers info.

Big difference between your Grid tie and a Hybrid system. You must have missed the comment about the cost of the Batteries.

MikeSus

Re: New to Solar

Blackcherry04 wrote: »

Big difference between your Grid tie and a Hybrid system. You must have missed the comment about the cost of the Batteries.

Yup didn't catch that but the idea still remains, lg panels for $370ish (20 of em) and a Sunny Island for $4200ish is $11600. That would still come in about $3k less with batteries.

jcheil

Re: New to Solar

MikeSus wrote: »

Yup didn't catch that but the idea still remains, lg panels for $370ish (20 of em) and a Sunny Island for $4200ish is $11600. That would still come in about $3k less with batteries.

Considering I do not sell or install solar for a living, my $30k amount was pretty much a "guess" just based on battery and panel prices. So I guess i am a pretty good guesser if I am only off by $2-3k
But that extra $2k will likely be eaten up with wire, breakers, mounts, etc.

Was just trying to let the OP have an idea of what they were asking for.
My system ran me about $8k last December and I did ALL of the labor myself and I am not using "great" batteries, nor a "great" inverter-charger; either which saved a ton of $, although I am sure in 5 or 6 years I would have wished I did.

MikeSus

Re: New to Solar

jcheil wrote: »

Considering I do not sell or install solar for a living, my $30k amount was pretty much a "guess" just based on battery and panel prices. So I guess i am a pretty good guesser if I am only off by $2-3k
But that extra $2k will likely be eaten up with wire, breakers, mounts, etc.

Was just trying to let the OP have an idea of what they were asking for.
My system ran me about $8k last December and I did ALL of the labor myself and I am not using "great" batteries, nor a "great" inverter-charger; either which saved a ton of $, although I am sure in 5 or 6 years I would have wished I did.

Excellent guess! Our guys actually came in better than what I could cobble together, so there are deals on quality stuff here in AZ.

Blackcherry04

Re: New to Solar

The cost of a Solar install is more than the sum of the equipment cost. You can't make a quality roof penetration for less than $30-$50 each and that's at least 2 for every 2 panels depending on loading.

jcheil

Re: New to Solar

Yeah that's a very good point, especially if you have to deal with the installation being to code.

MikeSus

Re: New to Solar

Blackcherry04 wrote: »

The cost of a Solar install is more than the sum of the equipment cost. You can't make a quality roof penetration for less than $30-$50 each and that's at least 2 for every 2 panels depending on loading.

Good point. Racks too. All that "little stuff" adds up.

I would definitely look at a few quotes if you aren't doing it yourself tho. We were surprised at the range we received (and the quality of the materials) Not everyone that comes in lower is using older cheaper panels.

MikeSus

Re: New to Solar

Stdyhand wrote: »

First off some history. My in laws are wanting my wife and I to move to Arizona so were planning to do it.

What part of AZ?

Rossman

Re: New to Solar

MikeSus wrote: »

Good point. Racks too. All that "little stuff" adds up.

No kidding man, and stuff might not be so "little"...I saw a quote for a system the other day, the PV panels were about 6grand, but the racks to support them were also like 6grand. So that's like double the price just for racking them up!

BB.

Re: New to Solar

A few years ago, we were using $1 per watt for racking costs for back of envelope calculations... So, yea, the racks cost just about the same amount as the solar panels (excluding labor).

When panels where $5-$10 per watt, the racking costs were not a huge deal.

-Bill

Stdyhand

Re: New to Solar

Fridge burning 24/7, my 52" tv, two computers, one 22" monitor, 3-4 lights, and smaller stuff being charged have managed to burn about 41KwH the last 3 days. I held off on all laundry, kept the lights off as much as possible, and still managed to burn that much power. I did find the electric dryer is a demon that should be exercised. My larger tv and PC tower I built are also killing me. The most the fridge has used is 1.5 KwH in over a day. The large tv and PC used almost 2KwH in a few hours of doing nothing but reading these and other forums. For this reason I'll be getting a new laptop for web activity.

I am confused on battery storage though. Correct me if I've got the math wrong on this, but I got the 1.5 fudge factor from another forum so I'm assuming it is referring to inefficiencies. I am also calculating for roughly 4 days of capacity with a 50% discharge IF we ended up going that long with overcast. Of course I would use a generator to recharge a battery bank before it started getting that low. I was also planning on a 48 volt system, but not sure how I can do that and keep as few batteries in a bank as possible. If this is not wrong, maybe you can help me understand the battery capacity a little better or point me somewhere I can read about it more.

13000 watt hours x 1.5=19500
4x2=8 days

19500x8=156000

156000/48=3250 amp hours

What is the best way to achieve this storage capacity and maintain a healthy battery bank? I was considering using Trojan L16H-AC batteries. They have a 435AH rating if I read that correctly.

How would I go about achieving this much storage?

Sorry if you've been asked this a thousand times but I've been reading so much lately I feel like a discharged battery myself. I'm a bit stubborn in that I want to learn this and don't tend to rest until my mind is confident I understand it. I'm not big on paying someone else to learn and do something for me when I can do it myself, so I appreciate the knowledge shared here.

NorthGuy

Re: New to Solar

Stdyhand wrote: »

How would I go about achieving this much storage?

You buy 64 batteries and install them as 8 parallel strings of 8 batteries each. Or you look for bigger batteries.

I have about the same consumption as yours, and I'm doing fine with 673AH of batteries (about 20% of what you want), and would be doing even better if they weren't Trojans.

Stdyhand

Re: New to Solar

The Trojans were a consideration before I realized my power consumption. That is not set in stone. I am using them as a reference to help me understand battery capacity. I'll decide for sure on equipment once I've gained enough knowledge on this, but so far I'm a bit shocked at the number of batteries it takes to store power.

Vic

Re: New to Solar

Those particular Trojan batteries appear to be Floor-Scrubber machine batteries. They have quite a lot of capacity, but it is quite possible that they will not do so well in an RE environment -- where batteries need to supply quite a bit less power, but over a longer period of time, and be recharged fairly slowly. Floor scurbbers often deplete batteries essentially completely in a few hours, and have the snot charged out of them in not so many hours.

Glad that you are not married to those batteries.

It is very good that you are trying to get your head around all of the off-grid issues BEFORE buying anything.
Just my opinions, Vic

NorthGuy

Re: New to Solar

Stdyhand wrote: »

... so far I'm a bit shocked at the number of batteries it takes to store power.

That is because you sized them for 4 days.

Imagine you bought all these batteries, which are supposed to take you through 4 days of cloudy weather, then there's a fifth day, and it is still cloudy. Do you have a plan for this situation?

newl

Re: New to Solar

Of course I would use a generator to recharge a battery bank before it started getting that low.

He did have a plan indeed.