Net Zero Energy In the City

[gizmo23337]

I'm new here, so I'll give a quick intro. I'm an electrical engineer of 10+ years, specializing in digital printed circuit board design, and DC/DC converters. I bought an older 50's house last year, which is in a rural residential area which is near an industrial park. I've had a year to watch electrical usage and am making some changes to move towards a balanced energy budget. My goals are tiered, and I'm not sure what I can achieve just yet within a limited budget. First goal is to lower power bill. Second goal is to eliminate or turn profit on power bill. Ultimate goal is to pay off both hydro and gas bill and break even or better.

First, I have a grid tied house, so living off grid and battery storage are not things that I need. I do not intend to have power in my house during power outages. In fact, with a new firehall across the street, we are out of power for maybe a couple hours a year in this location tops.

Phase 1 has already begun which is measuring and lowering our consumption within reason. When we moved in we had an oil furnace with an electric plenum heater. So far the heating has been switched to gas, and we intend to use the rebates to swap to a gas hot water tank and dryer over the next couple of months. I won't post the electrical numbers from last winter because they are quite embarrassing with electrical heat, but with the new gas furnace we are near 24kWh/day heading into November. I changed light bulbs to CFL, set up proper timers on computers for power management and will be installing a few key switches to help with parasitic power to entertainment and computer areas. With the additional hot water, dryer, bulb, and other minor changes, I'm guessing I can get our usage down to ~15 kWh/day. I am monitoring this, and this will continue into the spring before I move on to the next phase.

So, thinking ahead to phase 2, I'd like to add some solar and/or wind. The net metering program pays out 8cents/kWh, which is better than tier 1 at 6.5cents/kWh they charge out at. For an installation <5kW, the connection and permit process is cheap and easy. For BC, the expected solar output for 1kW solar is about 1200kWh/year. Our location has great southern exposure with 1/2 acre clear in the backyard. With those numbers, something around 5-7kW of solar should be close to breaking even or a profit? I'd like to turn a small profit to put towards the gas bill. I consider breaking even on both the gas bill and hydro to be the holy grail scenario, but I'd be plenty happy to get those bills combined to <50$/month. I'm expecting our gas bill to rise to ~100$/month initially.

Phase 3 might be adding some wind power. My location is partly ideal, but I'd have to compromise at 60ft height and consider convincing the neighbour to top some trees. Typical wind speed here is 3.5m/s average. I'm not worried about the average though, its mostly the feb-may months where is it very windy constantly (when there is little sun). In recent years with climate change, we have noticed a shift. Weeks of uniterrupted sun in the summer, and a longer windy spring. In february, it often blows for days on end as we are near the ocean.

I have many questions as to how to proceed, and may have something to contribute by the time I am done. I will gather some site photos and lot layout so I can get meaningful help. At the moment though, at 15kWh/day usuage, what is the optinion on how much generation I might need, and how to split it. I may very well add 1kW solar at a time twice a year, or something like that.

[DamonHD]

We are net-zero or net-negative energy at home.  Though we now have a lot of PV on the roof, the biggest moves towards our current position were by cutting electricity use about 6-fold and natural gas use about in half.  Conservation ("negawatss") is the cheapest renewable energy source.

http://www.earth.org.uk/

We're on about 4--5kWh/d for electricity and about 10kWh/d averaged over the year for natural gas, here in London, England.

Have fun!  B^>

Rgds

Damon

[jn_austin]

I used a bunch of 245W panels and Enphase microinverters for a grid tie system. I am sitting in a similar situation trying to reduce the overall bill to near zero.

First off do a comprehensive energy audit. That 1950's style house probably leaks around all the windows and may be poorly insulated. We live in the south so solar screens alone saved us about 10% on our bills. Low wattage lighting and good sealing doors and windows along with every light plate, outlet, duct, and crevice that could potentially leak were addressed. Had to have a whole house energy audit guy come out do do the lakage tests but it was well worth the cost. Amazing what a little caulk will do if you add up all the leaking places.

After the home is sound then work on the solar. WE have a large array and it only covers about 1/3 of our total bill. I have decided to expand the system and it should get us closer to net zero but only at certain times of the year. As I see it the electric rates are only going to go higher so why not spend my money on an investment that will guarantee some payback. Can't say that for the stock market! SOlar in general is not cheap to install to get to net zero. The second array is scheduled to go live in about three weeks so I will know then how close I will be to zero. For sure in the cooler months I will be in the black but the make or break months of summer will be the real test.

BTW - I used to do PCB's years ago. A lot of fun. I still do hobby boards from time to time. An EE for 20+ years here!

 

[gizmo23337]

Well, our average for the first year (in the worst possible scenario, including first winter in a crappy house with electric plenum heater), had us at ~60kWh average per month. Worst month was almost 3500kWh, with 640kWh/month in the summer. I installed a high efficiency gas furnace, and with rebates and everything included, I should end up paying that furnace off by spring (4 months). Our average is now probably between 20-26kWh/day now? With the hot water, dryer and other upgrades, I suspect we will enter a 15kWh/day range, or better for electricity. It's a 2000sqft house with 2 adults and 2 kids full time and 2 additional kids part time. I can't expect them to conserve too far other than being the light hound and turning things off myself.

I installed new weather stripping, door jams, plastic storm windows, and sealed up many of the heat leaks, to help with that gas furnace. There is more spots I can increase insulation, so that is on my mind as well. In summary, I am in conservation upgrades and monitoring mode. I totally get generation costs way more than conservation.

Has anyone thought of doing vacuum evacuated solar heating tubes hooked up to a generator? I think in theory they capture more energy than solar panels, are an order of 10 cheaper, but there would certainly be losses along the conversions needed. I need to do more reading about this. The good news is I am still in upgrading/conservation mode, so I have time to read and think before spending. Ideally, I'd like to find a way that doesn't take 10 years to pay it self off. 3-5 years would be a good number imo. Btw, thanks for the feedback. Interesting to hear other stories and that it can be done 
Also, when I'm saying net zero, I'm meaning net zero cost first, but total net zero energy would be even better.

[SparWeb]

Hi
Welcome to Fieldlines.
I made a number of changes like you have, a few years ago.  You've done well for streamlining your house.  Changing the furnace and sealing up the corners of the house is already way more than many people do (including me).  I haven't gotten around to the furnace project, but less pressure on me because I already have natural gas and seem to use 1/2 the energy as my neighbours.  Don't forget the programmable thermostat.  If you have one, just haven't mentioned it, then you already know that turning the heat down overnight automatically can save a bundle of energy, too. 

You sound like the type who can deal with a wind turbine, and will know what to expect.  It's a project and a half, even if you buy the machine, because there's still the raising of the tower, and subsequent maintenance to take care of.  You may find solar just as rewarding, and probably more profitable.  I usually recommend wind turbine projects to folks who are both equipped for it and interested enough to carry through to the end.  If you're one of those, then you have found a great place to get ideas and inspiration.  I also try to bear in mind that if building my own wind turbines was not my hobby, then I'd spend money on some other hobby instead.  So if I'm going to spend money on a hobby in any case...  then at least there's a useful product in the end.  Plus, I have avoided a bunch of buried cable excavations to have electricity in my barns, by putting solar panels on one, and a wind turbine beside the other, instead.

I have a few solar panels up, and a DIY wind turbine.  I'm on the grid too, but without incentives (in Alberta) my RE stuff isn't grid-tied.
Basically I work on things on the cheap, because it's just a hobby to me, but handy to have when the grid is down (1-2 days per year here).

Keeping an eye on the dollars, watch out for "fees".  Just because the utility company is paying you for the kWhrs, doesn't mean they won't claw back some.  You are being given the "privilege" of supplying the grid with energy, after all.   

Depending on the kids, a little bit of greenhouse gas / global warming propaganda can go a long way.  Some kids are deaf to that stuff, though.

Heating with evacuated solar tubes:  Since you just replaced your furnace, I assume you don't mean space-heating, though you certainly can do that with solar-thermal panels on the roof if you want.  I think you mean heating your water with solar thermal, and in that case there are a number of these systems designed as a "package" on the market, and installers in major cities who can put it all together to suit your house.  I won't know who to recommend in BC, but maybe it will only take a bit of asking around to find the right professionals.
Are you currently heating your water with natural gas or electricity?  If I were to make an estimate, I need 0.5 GJ per day of natural gas for the hot water heater.  Over the year that is 182 GJ, and at 3$ / GJ, it costs me about 550 dollars per year for my hot water.  What this ballpark number does, by showing my annual costs, is help judge the value in reductions of that consumption.  Maybe these figures will be useful to you, too.

[keithturtle]

Are you currently heating your water with natural gas or electricity?

Yeah, that water heater and clothes dryer account for most of the usage.  Got a basement?   Hang up the clothes on a line and run a dehumidifier, lots less kWh consumed.   Switch the WH to gas and save at least half.

At least that works here

Turtle

[gizmo23337]

It's funny, because my professional area of expertise is ultra low power circuit design. I started out my career years ago at Nortel Alberta, so I understand that prices and rules are different depending on your area. Only recently have I decided to take things personally and bring low power into my home. Then again, a couple of $800 power bills will make you wake up and want to change things in a hurry.

I'll probably attempt a wind turbine, just because it interests me and could produce something useful. My location probably falls into the category where I could get lots of power for a few months a year, but it would have to be built like a brick because the turbulence would bounce the thing around. Going more than 60 feet just isn't practical for me. In Ontario, they pay a home owner 80c/kWh specifically for home roof mounted solar panels up to 10kW (and guarantee that rate because they sign you 20 year contract). I could see our local utility paying more than 8c/kWh in the future, so if anything I'd expect an upward trend. Smart meters just got installed province wide, so peak hour billing probably isn't too far off now. The two generations before me in my family worked for the utility company, and the utility hasn't invested in any new sources in 30+years. Basically, they turned into a billing company, and only now have reached the panic state where they are not meeting demand recently. This could only mean higher billing rates, and we are seeing that now starting with two tier billing.

The kids are tough to teach and most of it is laziness. The younger one is too young to remember, and the teenager doesn't care about anything except Ipod, Internet and laptop. I'll wake up in the morning and both bathroom lights will be on because two kids got up and used the wash-room and left lights on. I'm thinking about installing motion activated timers in a couple key spots to deal with this, but I'm not a big fan of them. I wish I had some sort of Bluetooth or distance sensor necklace where the switch automatically goes off when nobody is in the room. The problem is, the sensor itself would draw power, but maybe that could be a reasonable trade off. In the short term, they are now CFL bulbs, and in the spare bathroom, I only put half the bulbs in to help even more. That bathroom is only used at night anyway, so even the night light outside is almost enough.

As for the solar water heating, I currently have electric water tank. I was planning to change it to a gas water tank with the rebate from the furnace. If I plan it right, it could be useful to pre-plan for a solar/gas water tank system. My new gas furnace is pre-planned for a heat pump. I have the coil unit sitting on top of the gas furnace so I didn't have to re-do all the metal work. All I have to do is plop the heat pump outside and run the copper tubing to the coil unit. Thanks for the water numbers, I want to start monitoring water and dryer individually now that it has been mentioned. I don't have any real data on what part the water is for my bill. The kids are terrible with showers/bath/dishwasher and terrible for laundry. Interesting idea on the de-humidifier. I'd try that perhaps if I had a wood stove in the basement, which I don't at the moment.

What I was wondering if anyone has thought, done calculations, or attempted a solar evacuated tube "generator". Key parts would be the evacuated tubes, a tank/boiler unit to contain the heat, a steam or Stirling type engine, and a wind turbine generator. Perhaps the tank could even be a hybrid storage system which could dual as a hot tub. I realize there is a bit of dreaming going on in this thinking. A 30 tube evacuated tube unit calculation typically shows 7kW worth of water heating. In some installations, they have to install cooling (heat sinking) because the hot water is scalding hot. Such a system might be complicated, but in my mind perhaps half the cost of solar panels, and more interesting (as hobby) than installing 10 grand worth of solar panels that might pay off in 10-20 years. The other simpler option might solar evacuated tubes connected to peltier elements. If I could find cheap peltier's by the hundred, this would be the way to go for sure (less moving parts).

I have designed some battery chargers and similar before. For those that are interested in PV MPPT on the cheap and simple, you might want to check Linear Technology energy harvesting and their demo kits. There is some nice stuff there and some of the demo kits are only $15. I have no affiliation with them other than buying their stuff as an engineer, and I don't think I should post links.

[SparWeb]

... attempted a solar evacuated tube "generator"...

Oh, I think you mean a solar steam turbine, to produce electricity.  Tricky...  Have to think about it...
High pressure and noise...  Even if it is possible, it's probably not safe nor quiet for the residents of the house.
...Instead of just saying "no" I'll stick with "caution" until I better understand your idea.


I laugh at my kid too, turning on bathroom lights to pee in the night.  There's a night-light in the bathroom already, he can aim/fire no trouble with that much light, especially with dark-adapted eyes.  But NO, he has to turn on the bright light and squint for a minute.  You can't explain this to them, either.

This month's HomePower magazine has a feature article on hydronic home heating.  You've already got forced-air, so that's not relevant to you, but the other half of the system (tubes and hot water storage tank) may be of interest.


If you're ever going to be in the Calgary area, drop me a line.

[Mary B]

Put led lighting in those rooms, half the use of a CFL. Far enough north in winter you don't need to dehumidify a heated basement. With the heat on house humidity can drop to 20% or less.

[birdhouse]

i don't know if it's the same in canadia, but here in the states, roughly $900 worth of blown in attic insulation gives a free blower rental at (home depot). 

the $900 worth of either cellulose or fiberglass would give most any home (<3000sqft) a HUGE advantage for heating AND cooling.  just make sure you don't blow shut the "air intake" from the eaves/soffits.  they make special styrofoam panels to elongate those air venting regions above the insulation level, while allowing the insulation to be thicker than thick, yet below the venting extensions. 

i've wanted to do this to my home for quite a while, but just end up splitting more wood instead (wood stove). 

adam

[gizmo23337]

I'm skeptical on the LED lighting. When I read the label, I don't see much power advantage, although I have not done direct measurements myself. The supposed advantage is better life, but at 4 times the price I can't justify it. An advantage is you could use dimmers and lower the consumption which you can't on CFL.

As for my idea of solar evacuated tubes to drive a generator, it is sort of based on this idea:
http://www.youtube.com/watch?feature=player_embedded&v=uqQVyRaHXIk
http://www.youtube.com/watch?feature=player_embedded&v=ZEnqQxFeS74
I was trying to think of a way to use evacuated solar tubes to bridge the gap to steam. The price point *maybe* better than solar panels if done right.

I'll post some site shots I took a bit later. I have to shrink them to proper size first.

[gizmo23337]

Ok, I've attached my site locations. The winter looks so depressing around here, and this house needs more upgrades . 


In the first pic, this is looking north at the roof (which is south facing). Old oil furnace is outside so I can rip out the fan motor and recycle the metal. Nice pile of black walnuts heading to my "free stain" bin, and tree farm seeds. I went up on the roof, and noted that the new furnace exhaust out the chimney is not hot, fast or useful for anything. When they say these new furnaces are efficient, I believe it!

The neighbour on the other side of the duplex has a nice wood stove vent that has waste heat though. That satellite dish, could be converted to one of those big ugly dishes on a motor? I could aim it at solar water heater during the day and then point it at the tv in the evening. What better way for the kids to understand power management. "You haven't charged up enough to watch TV yet, so go outside and play while the sun is shining"!


In the second shot, my concerns about distance for wind generation from the trees. The closer ones past the shed lose their leaves, and are about 200? feet away. The evergreens are likely over 700ft away and less of a concern. This is the opposite house facing shot to the south, and the wind always blows from south'ish towards the house in the spring. This is also very nice growing space which is in the process of getting cleaned up. When I moved in, the grass was 6 feet high. Those blackberries need to go, but at the moment we have free, sweet tea.

[birdhouse]

just from a contractors standpoint:

you've got stucco.  yet the first floor has decent over hangs, so YAY! 

the basement under the deck is GOING to be a problem if it isn't already. 

some basic flashing could divert water enough to mimick the eaves of the first floor. 

keep that water away from that stucco.  wind driven rain is one thing, but constant seeping down (below the deck) is bound to give issues. 

just some thoughts

adam

[gizmo23337]

That basement over the deck is my master bedroom at the moment, and not leaking.. yet. I plan on re-doing the deck, and extending a clear plastic roof over the deck to the deck railing to help with the water from above. The bottom ground level is paving stones with plenty of weeds. This will be concrete slab draining away from the house soon. Most of the moisture at the moment is from the water running off the deck and then sitting on the ground below. Gutters and a roof above would help a lot.

This will all get done in due time, so I want to talk about pointing a bigger dish at my non-existent evacuated water tubes to boil water and turn a wind turbine lol. If I do it right, it could pay for the deck. I'm optimistic, handy, and have taken on a big project with this old house. If I can make this thing break even on energy bill, then anyone should be able. I'm still optimistic I can achieve close to net zero cost (with the gas of course).

[birdhouse]

have you contacted your electrical supplier yet? 

typically they charge $30-$50 a month for the "privledge" to give up your juice at 8cent a kwh you quoted???  8 cents month might mean you need to create 500Kwh a month just to break even?? 

maybe canada is different...   what's the case? 

adam

[gizmo23337]

There is no extra charge to generate at the moment, and they gladly come put the meter on your house for free, for the privilege to generate as far as I can read and tell. Would love to have the 80c/kWh rate from Ontario though

I must be doing something right so far, because the utility installed a smart meter in the spring, and they came to calibrate and read it last month. (seemed a little low/off because I was on the low side, 65%+'ish below average history).

For the insulation, its actually pretty good for the roof. That room under the deck has little hope at the moment, but the front garage needs help and I'll save that for another day. In summary, its a single metal door that is one piece. There is a crack at the bottom. Its thin metal, and leaks heat, so I need a sub wall or insulation on that back of that. It's one of my final pieces of sealing up this place for the winter.

I only have a few hours a week to make changes, so I have to pick wisely.

[Mary B]

Typical 40 watt CFL is around 13 watts, LED was 6 or 7 watts

[ghurd]

i don't know if it's the same in canadia, but here in the states, roughly $900 worth of blown in attic insulation gives a free blower rental at (home depot). 

Doesn't take anywhere near that much here to get the free blower.
Toyota Tacome with a cap got most insulation in 1 load without careful packing effort.
2nd load was the rest of the insulation, and the blower.

Blown in on top of fiberglass can be an issue.  The blown in weight compresses the fiberglass so that must be accounted for.

Insulation is always good.
G-

[DamonHD]

Insulation is always good.
G-

Seconded.

Rgds

Damon

[gizmo23337]

My insulation in the attic is good. There is no insulation in the garage wall, and possibly none in that back room under the deck. In fact, my inside garage wall isn't even attached to the ground! In any event, I'll agree that money spent in insulation is worth more than generation.

[birdhouse]

for a five minute fix, you might throw a bit of that aluminum HVAC tap on the inside of your cracked garage door.  atleast create an air barrier. 

you're obviously on the right track.  FYI: current building code where i'm at for ceilings is R-40 or 49...  i forget... 

i recently did a job where the client spec'd R-60 in the attic, and they've been extremely happy with their natural gas usage during the winters!

adam

[richhagen]

A couple of notes. 

Currently, the best LED bulbs I have seen commercially available are Phillips 10 Watt Bulbs at 940 Lumens and with a reasonably warm color temp.  I have six of these in use in my home to test.  I have  been keeping an eye on these as they have been improving.  Those bulbs still cost around U.S. $30 a piece though, so they will not pay for themselves vs. compact fluorescents for general A19 bulb replacements where you can get a roughly equivalent 13 Watt compact fluorescent bulb for under a U.S. buck although they are not rated for as long of a life.  You can probably get a better return where directional lighting is required with specialty bulbs though as LED's tend to be inherently directional.

I have been installing dual level lighting with motion sensors in one of my buildings hallways and have found that the motion sensor from Lithonia lighting generally draw around 1 Watt, around 8 mA AC, continuous when inactive.  I have sensors from Heath and Lithonia installed there at present, and for my purposes, one bulb in the fixtures is on continuous and two more turn on when motion is detected.  I am hoping that over the next 12 years the lights will pay for themselves relative  to equivalent non-motion fixtures.  It is not a quick pay off because of the extra wiring and electronics relative to the cheaper commercial electrical rate I pay there.  If electricity rates shoot up faster than anticipated, then the time will of course be shortened.

[gizmo23337]

Part of my equation for light bulbs has to do with winter storms, power outages, winter car accidents (and power bumps), and power surges.

I swear that the winter kicks the nuts out of the bulbs with power bumps and shortens the life. This is my biggest reason for not going LED at the moment over cost. That 2-4 times the life will never happen for me. It might for a different person somewhere else though, with milder weather.

[ghurd]

The LED bulbs with input rating of 85~250VAC should handle the bumps just fine.
G-

[Mary B]

The power bumps and surges were giving my CFL lighting a 1 year lifespan at best, my LEDS are going on 2 years and one tends to be on 24/7 because that room(bathroom) is dark and gets used often.

[gizmo23337]

I'd like the led/cfl discussion to continue. I could be convinced, but there isn't enough data yet. Ultimately, when the price drops enough, I think the debate will be over and LED will win.

For my garage door. It's a single sheet of metal from the 50's, one piece, and slides up and down (not the folding type). There is a gap at the bottom. I have some rubber industrial wall trim that I can install with metal screws at the bottom. This would block the 1/2inch gap, but the cold still comes through. I have options of installing another wall behind the garage door, putting some foam and other insulation on the back of the door, and/or fixing the insulating wall at the back of the garage. There is duct work and some gaps at the top of the wall, and no insulation on that inside second wall. There is a lot of cold sneaking in through there which I'd like to fix. I don't know how I'd attach foam to the back side of an irregular back of the garage door. Its not flat, so it wouldn't be easy. I'll try and post pics soon.

[thirteen]

Could you use spray on foam? 13

[DamonHD]

Chances are the concrete/cement floor of the garage at the entrance is a massive thermal bridge, which you'd have to interrupt in some way to significantly reduce heat losses once you've done the rest.

Rgds

Damon

[Mary B]

There are spray on foam kits you can buy. I used one to insulate my foundation.

[thirteen]

to get to hard places to reach I got a longer piece of tubing and extended the nozzle into hard to reach places. But figure out where you will use all of it in one setting  for from the can it doen't take long to have it setup. 13

[dgd]

I'm skeptical on the LED lighting. When I read the label, I don't see much power advantage, although I have not done direct measurements myself. The supposed advantage is better life, but at 4 times the price I can't justify it. An advantage is you could use dimmers and lower the consumption which you can't on CFL.

I have changed my 3 bedroom house from mostly cfl lighting to led lighting. There are real power advantages with LEDs, most of my LEDs are 3, 4 and 5 watt in gu10 fittings. Dimmable too.
In lighting stores these can cost about $30 to $40 each but in the last few months we are seeing much cheaper, $4 to $8, gu10 led light coming from Taiwan/China and quality looks impressive for the cost.
Shop around, try eBay..
Dgd

[Mary B]

There are kits you can buy with disposable nozzles. Remove the nozzle when finished, clean the hose ends and good to go for the next use. Can probably find a better price, I just grabbed one of the first links

http://www.foaminsulation.net/spray-foam-insulation/spray-foam-insulation-kits/handi-foam-quick-cure-closed-cell-insulation-kit/

to get to hard places to reach I got a longer piece of tubing and extended the nozzle into hard to reach places. But figure out where you will use all of it in one setting  for from the can it doen't take long to have it setup. 13

[gizmo23337]

I like the idea of the spray foam. I'd have to leave gaps for the sliding door locks, but that is ok. Still much easier than cutting pieces of foam. I will probably increase the R value of the house wall that meets the garage as well, which should be a big improvement.

I am still waiting for my next power bill to see where our new base line sits. I have good numbers for a full year now to compare. I'm expecting us to level out about 24kWh/day with just the CFL bulb, and change to gas furnace. TH\he next two winter bills should really tell the story. I will probably have to wait till spring before the furnace rebate shows up so I can install gas hot water and dryer. My other option is heat pump as I already plumbed in the coil unit, but I think my short term gains are better in the hot water and dryer.

In the mean time, I have been looking at diy solar air heaters, since the cost and complexity is very minimal. I like the three screen design, and efficiency looks as good or better than many of the other designs. I am not sure we get enough sun in the winter for it to be worthwhile. We are entering windy season, so a windmill would be more practical, but I just don't have the time or resources for that project at the moment(especially during holiday season). The solar air heater could at least heat the bedroom under the back deck, which is dual purpose as my Lady's art room/office.

I've also been pondering buying the solar water evacuated tube setup. It would help in the spring and fall for sure. Both the waste hot air, and extra hot water in the summer could be tied into a diy hot tub. In fact, I was looking into wood fired diy hot tub, and have an idea for a brick fireplace out back beside a hot tub with heat exchanger. I could bubble waste hot air through the hot tub water, use the waste solar water, and additionally fire to heat up a hot tub quick during the summer(three heat source setup). I'm the kind of person that would fill the tub up in the morning, put a rotisserie on, some meat in the smoker, and have a bunch of people over to sit in the tub all afternoon. No chem, just heat the tub up, use it in the afternoon and then drain it out into the garden.