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Powering Your Off-grid Lifestyle: How Solar Compares to the Competition

 
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If you're living or building off the grid then you no doubt know how difficult it can be to keep your building warm during the winter. From wood burning stoves to propane heaters to biomass boilers, there are a variety of ways you can heat your building, but one often overlooked method is solar heating. While using a PV system to generate electricity is a fairly common practice among those living off-grid, using the sun to heat your building is less common. However, if you're off-grid, a solar heater is often not only the greenest option, but the most economical as well.
SOLAR THERMAL COMPARED TO FUELS
When comparing dollars and cents the upfront cost of installing a solar heater are usually higher than the cost of one of the fuel alternatives, though you'll find that some high efficiency burners cost more than a comparable solar heater. However, the running costs of a solar heater are nil, so if you're currently heating with a fuel source, or planning to do so, calculate how much you're spending on fuel. If you can reduce that cost by 90 %, how long would it take to cover the cost of a solar heater? You'll likely find that after a year or two your solar heater has paid for itself.

Another aspect to consider is the convenience factor of a solar heater. If you have to source and transport your fuel multiple times a year, that's time you could spend doing other things. Generally, a solar heater takes between one and seven days to install, depending on the difficulty of your install and your construction proficiency. Once installed, there's no upkeep or maintenance.
WHAT ABOUT USING PV PANELS TO POWER AN ELECTRIC HEATER?
If you've already got, or are planning to put, PV panels on your building you may be inclined to use the electricity they generate to power an electrical heater. Though not the worst option for heating, electric heating is much less efficient than solar thermal heating. Because the conversion rate from solar energy to heat energy is about 70 % whereas the conversion rate to electricity is only about 20 %, you need three times the space of a comparable thermal system to generate the same amount of heat.
WHY A FREEDOM WON SYSTEM IS BETTER THAN OTHER SOLAR THERMAL SYSTEMS
There are many sellers of solar thermal heaters, however our FREEDOM WON Solar Thermal Heaters are the best for off-grid applications. Most solar thermal heaters require an external power source to run the pump that circulates the heat transfer fluid from the collectors to the storage tank, however FREEDOM WON systems are self-powering, meaning they don't need to be connected to an electricity source. They also work autonomously, turning on when the sun shines and turning off when it doesn't without any input from you, meaning your property will stay warm even when you're away. The system also automatically gets rid of any excess heat, preventing vapor locks and stagnation, and meaning you can easily size your system to provide all the heat you need without concern for overheating in the summer. Finally, the system is virtually maintenance free. Once up and running all you'll need to do to keep it running for 25 plus years is to occasionally change the circulating glycol, generally less than once a decade. These features unique to FREEDOM WON systems make it ideal for off-grid applications.

Our patented FREEDOM WON systems are only available from Simple Solar and our authorized distributors.
 
pollinator
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Your efficiency for solar electric versus solar thermal pre supposed that you would turn that electricity into heat using a resistive type of heater. If you pair a solar electric panel with an air to air heat pump the efficiency will match a solar thermal panel and you can run it off the grid or battery power once the sun goes down.
 
pollinator
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If my solar hot water system is no good in winter, how does this system fair?
 
David Baillie
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John C Daley wrote:If my solar hot water system is no good in winter, how does this system fair?


Hi john were you asking me or the original poster?
If you are grid connected a solar electric system running a heat pump would keep going using grid power or batteries. I just found the original post left out some info to further a commercial argument.
 
master pollinator
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Nice sales script. All problems solved and everything is easy-peasy!

Alas, reality intrudes. I would like some hard data please. Latitudes where this will be effective? Square feet that can be heated in winter, and the temperature zones where that will be effective? Cost per BTU/kJ based on some baseline climate parameters?

This is of great interest. I hope you can help me understand how this may apply to my situation.
 
John C Daley
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David, my question is to the original poster.
 
David Baillie
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John C Daley wrote:David, my question is to the original poster.

my bad...
 
Harleen Aujla
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David Baillie wrote:Your efficiency for solar electric versus solar thermal pre supposed that you would turn that electricity into heat using a resistive type of heater. If you pair a solar electric panel with an air to air heat pump the efficiency will match a solar thermal panel and you can run it off the grid or battery power once the sun goes down.



Yes, a resistive-type electric heating option was anticipated.
The efficiency of the air-air heat pump depends on the ambient temperature and is known as Coefficient of Performance or COP.  When the outside air is only a few degrees below the inside air you may achieve a COP of 3.5 and in that case the PV efficiency multiplied by 3.5 COP will achieve the same efficiency as solar thermal, as you stated.
However the COP drops with the ambient air temperature and at -15C COP is down to 1.0. Air source heat pump (ASHP)units equipped for cold climates, such as the Mitsubishi Zuba series, include electric resistance heaters that come on when it gets cold. Therefore even with an ASHP you will at times be heating with electric resistance heating. This may be okay if you are grid-connected to a utility with low-cost green electricity but can be a problem if you are running on batteries, especially if you sized them assuming COP of 3.5!
Keep in mind an ASHP is a complex mechanical machine relying on advanced refrigerants with sophisticated controls whereas the Freedom WonTM solar heater is simple to operate with a small DC pump directly energized from a PV panel with no electronic controls and no auxiliary power required.
 
Harleen Aujla
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Douglas Alpenstock wrote:Nice sales script. All problems solved and everything is easy-peasy!

Alas, reality intrudes. I would like some hard data please. Latitudes where this will be effective? Square feet that can be heated in winter, and the temperature zones where that will be effective? Cost per BTU/kJ based on some baseline climate parameters?

This is of great interest. I hope you can help me understand how this may apply to my situation.


Hi Douglas,
We have some hard data that you can view with a system that has been running in the Canadian Prairies. I have pasted the link below for your viewing. Thanks
https://www.simplesolar.ca/tom.html
 
yeah, but ... what would PIE do? Especially concerning this tiny ad:
Saturday April 24th, 2021: Full Tour of Wheaton Labs!
https://permies.com/t/158985/permaculture-projects/Saturday-April-Full-Tour-Wheaton
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