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Passive house using PV electricity for heating.

 
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For those following the thread Dacian explains alot of what is talking about in this video on kickstarter: https://www.kickstarter.com/projects/electrodacus/120a-solar-bms-charger-lifepo4li-ion-offgridrv-wit/posts/1145014

Lots of EE in the beginning but he makes some good comparisons on the efficiency of different passive solar options towards the end. I'm not sure how much that changes in cooling climates and when you factor in DHW? What are you doing for Domestic Hot Water anyway? My climate is 50/50 I was thnking ground source cooling heat pump, Geo Thermal dead too? Or PV tied minisplit? I prefer radiant ceiling?

I'm having a hard time digesting all this electrical and electronics, so I want to study all that...may have some questions after I try and catch up. So when is your system design going to be available to the public for purchase? I guess you will do an assessment for clients and let them know if being tied to grid vs off is more cost effective, and a pay back period, or are you just doing this for fun?

I doubt you can get an accurate cost analysis using PVwatts or SAM with your system?
 
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Terry Ruth wrote:
Lots of EE in the beginning but he makes some good comparisons on the efficiency of different passive solar options towards the end. I'm not sure how much that changes in cooling climates and when you factor in DHW? What are you doing for Domestic Hot Water anyway? My climate is 50/50 I was thnking ground source cooling heat pump, Geo Thermal dead too? Or PV tied minisplit? I prefer radiant ceiling?

I'm having a hard time digesting all this electrical and electronics, so I want to study all that...may have some questions after I try and catch up. So when is your system design going to be available to the public for purchase? I guess you will do an assessment for clients and let them know if being tied to grid vs off is more cost effective, and a pay back period, or are you just doing this for fun?



I must admit I did not think much about cooling since I do not need that here with this house. When I lived in the city close to here it was impossible without air conditioning in summer since it was top floor (realy bad thermal insulation in the roof if at all) and under my apartment was the mechanical room with hot water boilers for hot water and heating.
I just hated that apartment in summer.
There are not that many days usually with temperatures above 30C (it depends on the year) and records are at around 38C
Inside the house here I never get above +27C and that is quite decent I do not need air conditioning.
In my opinion geothermal is dead but it may depends on how cheap you can install an effective ground loop. It may be worth if is used for both cooling and heating not sure.
In my case geothermal is not an economical option. The PV array that I need for heating and all other parts are around 10k$ and can last 25+ years with no maintenance since is solid state no moving parts or hot fluids.
Geothermal can save about 60 or 70% of the electricity so I can have 1/3 of this solar array size and out of 10k$ (pv array is about 7k$) I can save at best $4000 and with that there is no way I can do a ground loop get a heat pump to last 25 years and install all the hot water pipes and quality hot water circulation pumps.
I think PV tied mini-split will be the more cost effective solution but you will need to check.

I'm of course doing all this for fun (there is no other way). For sure this is not a profitable business for me I can earn way more working for a large corporation as I did before.
But I want to enjoy life and do what I like to do . The Solar BMS will be ready for Kickstarter bakers in October and the Digital MPPT I will build one for me to test and then see if there is enough interest from others I will do a Kickstarter for that also if not I will find something else to do. I have a long list of things I want to do so is not a problem.
I do not care much about grid. The amortisation cost for my current equipment is at 16 cent/kWh and at the apartment I was paying 50$/month for 250kWh that is 20 cent/kWh (kWh was about 11 cent but there are some fixed cost and taxes).
I specifically selected a piece of land with no utilities since I did not want any. My target is to reduce my spendings so much that I can enjoy my hobbies and do not need to work all day just to survive.
I can earn as much as I want and it will still never be enough to enjoy life So I chose to go in the other direction and reduce the use.

Dacian.
 
pollinator
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Hi Dacean,

I love your DC resistance heating idea!

I like your build too, even if I have a few "beefs". This is head and shoulders above what most of the professional "green" builders are producing.

Keep up the good work!

All Blessings,
Bill
 
Terry Ruth
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Dacian, hear ya on living simple and getting out of corporate.

Here is a thread and post from an installer that discuss micrometers vs DC optimizer. Is this accurate? What is your take on them are they worth the COP and how they differ from the efficiency of your efforts? I've read the studies out of CA showing higher efficiency from west-south facing hybrids....are you facing any west? http://www.permies.com/t/45940/solar/micro-central-inverter

Let's start with the DC optimizers that you mentioned. You are correct they are are a bit of a hybrid product each module would have its own optimizer that finds that panels maximum power point, the optimizers are then connected to a central inverter that converts the DC into AC. They work very well for installations where multiple orientations are used or there are some shading issues. SolarEdge is the main DC optimizer company and they have a nice online monitoring platform where you are able to see individual panel production. The optimizers have a 25 yr warranty and the inverter has a 12 yr warranty with the option to purchase an extension. The upfront cost is slightly more than just a central inverter but the systems I have installed with these have been producing really well.

If you are looking at microinverters they offer the same benefit of the optimizers where each panel will produce its maximum power and shading on one panel will not bring down the rest of the modules. Except now the conversion from DC-AC takes place on the roof at each panel. This is nice if you do not have the space to mount a large central inverter. If you are looking at Enphase microinverters they also offer a nice online monitoring platform but if you want to see panel level details it costs an extra $299. Their warranty on the microinverters is also 25 yrs. Most likely this would be your most expensive option, but should be pretty close to an optimizer system.

As far as maintenance if you did ever have to replace an optimizer or micro it usually involves removing a few modules to access the problem child, which is not a big issue as long as you have that detailed in the contract that you sign will your installer. I have yet to have a micro fail and have had one optimizer that was bad out of the box.

If you look at central inverters a lot of them come with something called a dual MPPT input which would allow you to have two strings of modules with different orientations. The biggest knock is going to be if you have any shading. When you have modules connected in series to form a "string" of modules it is possible for shading on one or a few modules to bring the power of that string down even if some of the are not shaded. Most central inverters have a 10-12 yr warranty but also offer the option to purchase an extension. This inverter setup will be the least expensive option.

When you start to look at efficiency numbers all of the inverters will be pretty close. You really want to look at overall system efficiency and this is where a tool like PV watts is very handy. SolarEdge and Enphase both have white papers detailing their overall system efficiency compared to central inverters. Hopefully this helps a little, if you would more detailed information on any of these systems I would be glad to help.
 
Dacian Todea
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Thanks Bill.

Terry Ruth wrote:
Here is a thread and post from an installer that discuss micrometers vs DC optimizer. Is this accurate? What is your take on them are they worth the COP and how they differ from the efficiency of your efforts? I've read the studies out of CA showing higher efficiency from west-south facing hybrids....are you facing any west? http://www.permies.com/t/45940/solar/micro-central-inverter



Here is my video explaining why mppt is obsolete and may other technologies aimed at optimising the energy output of solar PV panels all this because of the huge drop in price of solar PV panels.
A typical 60 cells (250W) PV panel cost now around $200 having anything on it to optimise the power will not be cost effective.
I'm mostly interested in Offrgid and not grid tie so I do not care about inverters or micro inverters. As for DC optimisers in order for them to be cost effective they will need to be high quality to last 25 years and cost less than $30 (15%) for a 250W PV panel to make up for the 15% annual average they can get additional at best but since is about offgrid that will be useless since the unused energy will be way more than that. You can not use all available energy do to finite battery capacity.
https://www.youtube.com/watch?v=cKrh9tdXDX8
So there is nothing to optimise if you need more energy just by an additional PV panel that will produce way more for less than any optimisation method.

Dacian.
 
Terry Ruth
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Makes sense. You know any other sites that track PV cost? http://www.ecobusinesslinks.com/surveys/free-solar-panel-price-survey/

Been trying to learn SAM, and I sat in on the Turbine webinar at NREL yesterday. Very good! The new SAM is an awesome tool, has a learning curve tho. I ran across this incentive from DOE for innovators like yourself might come in handy you never know. Low interest DOE back loans for new tech,

http://energy.gov/lpo/services/section-1703-loan-program
http://energy.gov/sites/prod/files/2015/04/f21/Credit-Based_Interest_Rate_Spread_7.9.14.pdf

I have a call into my grid to clarify but it appears they have to give me a bi-directional meter, can't charge time of use or any other related solar fees, have to purchase energy I don't use at an average rate they charge per month OR @ 150% of that rate if I chose not to store it for winter use. There are some benes being grid tied and you don't need batterys or have to worry about loosing power you can not store or use that lowers your annual cost of performance. I think you have to compare what you can sell to the grid vs buy battery systems that depreciate and loss of unused power. I did learn you can depreciate solar systems over 5 years, 30% fed tax for solar and small turbine. State tax incentives too depending. That can all change, the fed stops in 2016 may get renewed. I've seen several that have been cancelled in 2015.

Not sure about CAN: http://www.dsireusa.org/

 
Bill Bradbury
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Here's an interesting article by RMI http://www.rmi.org/electricity_load_defection that you guys might find interesting.
 
Dacian Todea
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@Terry,

No I do not know websites that track the price of solar panels. There are sure a few. Most concentrate on the price of solar cells and those are so low that I do not see possibilities of much more reduction and even if that is the case there is not much savings on there. The glass and aluminium frame are probably the expensive part already and they are also heavy contributing to shipping cost. But those prices seems about right. One of my solar BMS bakers in US mentioned that he got a full pallet 24 PV panels 250W each at 82 cent delivered so shipping is included in this price.
Here in Canada with shipping included is around 1 CAD but CAD is quite low now compared to USD

@Bill

I do not think battery will be a solution for individual house that soon. And large grid batteries will probably be more and more common in the next few years to deal with the increase of solar PV connected to the grid.
Still grid price can not go up in the future even if they will sell way less electricity. They will need to restructure close quite a few coal power plants and make the grid much more automated and smart.
Off grid price starts to get down with LiFePO4 and will continue to do so so grid price can not go up since they risk completely losing the grid.
So I think grid will be the main provider of energy in the future but it will need to be much smarter with a lot of smart appliances (IoT) that will use energy based on availability.


Dacian.
 
pollinator
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Dacian Todea wrote:I need about 7 to 9kW of PV panels to heat the house 100% with solar electricity. The house requires in the worst month 1000kWh for heating and since the heating season is long it requires about 4.5MWh per year



Dacian, first, hats off for the homestead you built. Have you looked at pv direct-drive reverse cycle chillers? C.O.P=3-4 to 1 and they operate in very cold ambient temps.

Its nice to reduce the amount of fuel we use for occasional solar short-falls.

Pv heating and A/C in one unit, plus since its pv direct, the pv's output can be switched for agricultural irrigation, or whatever else you can load it into.
 
frank li
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I did see your resistive heater idea. And i like your spartan approach with an eye toward a slab of warm stuff and no moving parts. The forever house. Do/would you use solar hot air and the pv powered forever floor?
 
frank li
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Pv optimisers keep the pv output at constant voltage. Game over, where is a high limit thermostat and some wire?!
 
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Dacian, I do have to ask a question:

Why do you prefer electrical heating over hot water heating?
Hot water heating should be less expensive and more efficient (and uses far less energy to produce).

greetings, Sebastian
 
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From a geeky old electronics tech professional & long time passive solar heat & PV enthusiast perspective this concept is completely fascinating!!! Definitely need to return to read again soon & dig deeper. My immediate needs are simpler. Improving insulation & storing mucho hot water is my plan. Already have nearly perfect south facing windows. Small greenhouse & some passive air heaters. I really just want to build an outdoor hot tub/rocket stove/cob oven creation & play around with the giant fresnel lens:) Might as well warm the shed with it. (it's a nice shed)

Not sure how cost effective this heating method would be here but definitely interesting. Wondering if latitude has any bearing on it??? Seems like there might be a sweet zone. Sometimes though ... you gotta do it just 'cuz you can. Excellent!!!




 
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The main problem with using solar thermal panels is that they produce the least amount of usable heat right when you need it most (when it's cold out), and the most heat when you need it least (summer).

PV panels, on the other hand, produce the MOST energy when it's cold out, and PV is ridiculously cheap right now.

Some ideas to improve efficiency and (possibly) reduce costs.  Use a heat pump instead of resistance heaters.  This can produce the same amount of heat with 1/3 to 1/4 as many PV panels.

Another idea I've been toying with, use BOTH solar thermal and PV panels.   During the winter solar thermal panels might only produce water that is 40C/50F which is too cold to be useful for heating, but when fed into a heat pump can increase it's COP to 4 or higher.  This improves the efficiency of both the solar thermal panels and the heat pump, giving you a double boost in output BTUs.

A setup like this with an IBC tote could easily store  150,000-250,000 BTUs of usable heat.  If you had the tote in the middle of your living space you wouldn't even have to insulate it, just use the heat radiating off it for part (or all) of your heating.
FWIW IBC totes are rated to handle a minimum of 140F, however most if not all of them are made from HDPE which can handle temps up to 230F, I'd say 200F would be a safe temp, keeps the water below the boiling point, that's over 250,000 BTUs of usable heat.
If you're going to store water that hot, you might want to insulate the tank a bit, just to avoid burns if you get to close.
Hmm, depending on how hot you get the tank, you could possibly put pots right on top of the tank and use it to slow cook food.

To put that in perspective, 250,000 BTUs is roughly the amount of usable heating you'd get from burning 70 lbs of wood in a good wood burning stove, or perhaps 35 lbs of wood in a well designed/built Rocket stove.
 
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