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Renewable Energy Systems
The sun’s energy is enormous, providing Earth in minutes more than it can use within an entire year. At peak around 1 kW of energy falls per m2 of roof area, depending on you latitude and the angle of your roof.
Getting it into your house therefore makes sense, and you are already doing so through your windows!
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Renewable Energy Systems
Solar Electricity Generating Systems
Solar Thermal Hot Water
A solar thermal collector is not much more than a ‘hot box’ with a glass panel on the front. Heat exchange fluid passes through pipes inside the collector and take away that heat, to be stored in a storage tank for when the home owner needs that heat (usually mornings and evenings for washing and bathing). An electrically driven pump moves water from the collector side to the storage side.
These collectors are way more efficient than solar PV modules, as high as 80% in fact. Overall system efficiencies can exceed 60%. However, as often the energy source (heating oil, natural gas) is a lot cheaper than electricity, the value of that free energy (heat) tends to be lower than for solar electricity. If you are displacing hot water generated by electricity however, this is by far the best option for your roof.
Solar Air Heating
If you use air, rather than water in your collector, it can be used as a free source of heat. Take cold air from the house and use a fan to draw it through a glazed collector on your outside wall, with the fan controlled by temperature sensors. Free heat!
A Canadian manufacture of transpired air collectors, focused on commercial buildings.
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Passive Solar
Yes, heat passes through windows. Windows are complicated but the essential calculation is this: if more heat makes it through during the heating season than is lost to the outside due to the window’s low insulation levels, you are heating passively. If this is the case, put them where the sun shines (south facing in the northern hemisphere winter, north in the southern hemisphere) and let the sun shine in. How can you figure this out? You’ll need some help from an energy modeler or expert home builder or architect. Here's a more detailed resource.
https://sustainability.williams.edu/green-building-basics/passive-solar-design
Batteries
In reality the electricity grid you are connected to operates as a huge battery. If you generate your own electricity you can send it to the grid when you don’t need it, then buy it back when you do. How this works out financially depends on how much you can sell it for (if allowed) and any variation in energy pricing day to night..
A battery is really for grid scale use, keeping the grid operating smoothly from a voltage and current perspective and providing storage for renewables.
If you live in a place with no grid, or one where blackouts are a regular occurrence, then you can use a battery to store either grid power or your own solar power.
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This is a very rapidly moving field, with metal flow batteries, Li-Ion batteries coming to prevalence. Panasonic is one of the key players - their cells are inside of each Tesla battery back.
Wind Turbines
Unfortunately, unless you live right by the coast, or in a very open area, wind turbines don’t go well with houses. Urban environments create lots of friction and air turbulence and wind turbines need smooth, laminar wind to work properly. All that friction robs the air of its energy. Turbines are also best left on poles or towers – they can cause vibrations when connected directly to your home. Even vertical axis machines, ostensibly aimed at the urban market, haven't been successful.
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Paul Gipe is a well respected and seasoned Wind Energy veteran. Lots of information here on successes - and failures - in the industry.
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Air Source Heat Pumps, Ground Source/Geo-exchange Heat Pumps
Solar PV panels (or modules as they are called) convert the sun’s light into electricity through the use of mostly silicon-based semiconductor materials. An inverter matches this electricity to the grid and delivers it to the load closest by. Electrons go to the closest place where they are needed!
If you are watching TV or running your computer, those electrons will be solar-generated ones.
Conversion efficiencies are in the region of 15-18% on a system level. Let’s be clear – this is converting the available solar energy into useful electricity. Not fantastic, and that’s because the most prevalent silicon-based modules can only in theory make use of 33.7% of the sun’s light - the Shockley-Quiesser limit.