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Has anyone looked at self contained solar units?   I am just starting to look.  If that is not successful I will go with a natural gas radiant heater until the solar option is available.  I know Tesla is now selling solar shingles on their website for use in the USA.  I think they are about 5-7 years away from those being viable in a harsh cold climate and also being able to power a house combined with their PowerWall.

Edited by David Owen
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10 minutes ago, David Owen said:

Has anyone looked at self contained solar units?   I am just starting to look.  If that is not successful I will go with a natural gas radiant heater until the solar option is available.  I know Tesla is now selling solar shingles on their website for use in the USA.  I think they are about 5-7 years away from those being viable in a harsh cold climate and also being able to power a house combined with their PowerWall.

 

 

This may work in some cases:

 

 

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12 hours ago, David Owen said:

 

 

This may work in some cases:

 

 

 

These units on a single unit basis are the equivalent of a 1500 watt heater.  They need a clear southern exposure and will work well at a 46 degree latitude in winter  according to their response to me.

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5 hours ago, john.r.davies said:

But how far north (or south of the equator)?

For instance I'm at 54North,    Peter is 2 degrees south of there.

 

I am at 46 degrees.  Here is the gentleman's email address.  THey are very helpful:  adam@arcticasolar.com

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The direct solar system does look very interesting but I wonder how useful it would be for Colin's use-case, ie keeping his garage frost-free. Without a massive building structure (=heat sink), solar-generated heat during the daytime isn't going to be much use in the early hours when the freezing occurs. And repeated heating/cooling leading to condensation isn't ideal.

When looking at car storage (rather than personal comfort when actually working in the garage) controlling humidity will be the most important factor I think. The various 'tent' type systems (Carcoon, Cair-o-Port etc) seem to be the simplest/lowest cost way to do that if you have a typical free-standing garage, as they provide a continuous gentle airflow over the vehicle.

Nigel

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6 hours ago, Bleednipple said:

The direct solar system does look very interesting but I wonder how useful it would be for Colin's use-case, ie keeping his garage frost-free. Without a massive building structure (=heat sink), solar-generated heat during the daytime isn't going to be much use in the early hours when the freezing occurs. And repeated heating/cooling leading to condensation isn't ideal.

When looking at car storage (rather than personal comfort when actually working in the garage) controlling humidity will be the most important factor I think. The various 'tent' type systems (Carcoon, Cair-o-Port etc) seem to be the simplest/lowest cost way to do that if you have a typical free-standing garage, as they provide a continuous gentle airflow over the vehicle.

Nigel

 

True as a standalone.  I doubt it would be difficult to supplement the heater with stored solar energy.

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That seems to work on the same principle as a Trombe solar wall which I recall learning of at polytechnic almost 40 years ago.  The heat gain occurs outside and is carried inside.

Just did a quick search and this link came up https://en.wikipedia.org/wiki/Trombe_wall  and  

https://greenpassivesolar.com/2010/07/passive-solar-partial-trombe-wall-house/#:~:text=A Trombe wall is an indirect method of,absorb the winter sun’s heat energy all day. 

This system seems to lack the heavy thermal mass

Paul

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Yes the 'Trombe Wall' concept makes a lot of sense in the garage context as the thermal mass radiates heat gradually into the building overnight to keep the temperature as even as possible. If I was building a garage from scratch and had a choice of site orientation, that would make a lot of sense.

(Paul, like you I studied this kind of stuff nearly 40 years back! Although I've forgotten most of it. It's a bit depressing how little these well-understood, practical energy-efficiency measures have found their way into the building industry.)

Nigel

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1 hour ago, David Owen said:

Okay, based on that (and converting F to C), if correct, an un-insulated two car garage requires around 650w to raise the inside temperature by 1C. From that, we then need to decide whether we're talking about keeping the garage frost-free (say 5C min), or creating a comfortable working temperature (say 17C) whenever you want to work on the car. That then determines the size of heater (in KW) required to meet the task, and also allows the electricity usage to be estimated for those two use-cases.

For this non-insulated double garage, let's say you want to be able to work in there comfortably on a cold winter's day - say 0C outside. Easy: 650w x 17C (the temp difference) = 11 KW, which is a pretty butch electric heater. An 8-hour "shift" under those conditions will cost you about £13 in leccie to stay cosy(ish).

But to calculate the 'frost-free' use-case costs annually, you need to start with the number of 'degree-days' outdoors over the whole year for your location. There are various online datasets/calculators for this, I used https://degreedays.io/Tools/DegreeDaysCalculator. For my postcode (in SE England) the 2019 degree-days below a base temperature of 5C was 128, or 0.35C on an average day. For our uninsulated double garage at 650w/1C, that means consuming just under 2,000 KWh across the year to ensure the garage stays above 5C, at a cost of about £300. If you wanted to keep it at a balmy 10C, your costs go up to £1,600 and you're deffo right off Greta Thunberg's Christmas Card list.

Of course £1,600, or even £300, buys a lot of insulation. 

Nigel

 

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