It is my intent to use a combined passive/active radiant heating and cooling system. The floors in both of my buildings are concrete, which is an excellent medium to use radiant heating in the floor. Additionally, water cooled polypropylene mats will be installed in the ceilings. In the studio building is will be cast directly into the bottom surface of the floor assembly to cool the space below. Radiant cooling works best when the cooled surface has a direct ‘line of site’ to what needs to be cooled. (People) In the residential building the mats will be installed in a dropped ceiling system that will be more appropriate for a residential application.
Typical radiant heating systems are supplied by hot water that is heated by either a gas or electric water heater. Considering the lengthy southern exposure (200’+) of my building I plan to use a passive solar water heating concept. On the roof there is a ‘mechanical’ penthouse, which will contain fairly thin storage tanks, that will be heated by the sun. These tanks will supply the radiant heating… I intend to maintain an auxiliary electric or gas fired source at the end of the storage system which will monitor the temperature of the water, and should additional heat be needed the conventional source will kick in. Keep in mind though that the water that is being heated will still need much less energy to get to the required temperature to heat the spaces. Here is a link to a website where a guy built a ‘shed’ specifically to do this. www.builditsolar.com
Below is a description of radiant cooling that I got from the website www.toolbase.org
Radiant cooling systems rely on chilled water pipes to distribute cooling throughout a building rather than a conventional system that uses chilled air and ductwork. Radiant cooling systems rely mainly on the direct cooling of occupants by radiative heat transfer (heat transfer through space like the sun’s warming effect on an object in its direct path) because the pipes, which are commonly run through ceilings, maintain the surface at temperatures of about 65°F. Through radiative heat transfer, people in the room will emit heat that is absorbed by the radiant cooling surface. To manage indoor humidity levels and air quality, a separate ventilation system to supply fresh air is needed. Due to the ease of controlling water flow, independent control of areas of the home is relatively simple.
There are at least three methods of delivering chilled water in radiant cooling systems. The panel system is the most common of these. Aluminum panels that carry tubing can be surface mounted or embedded on floors, walls, or ceilings. Another, the capillary tube system, consists of a mat of small, closely spaced tubes that are embedded in plastic, gypsum, or plaster on walls and ceilings. Or, similar to hydronic heating systems, a concrete core with embedded tubes can provide the conduit and thermal storage capacity for a cooling system. In each of these systems, the water is mixed with glycol and cooled by an air-to-water heat pump, a cooling tower, a ground-source heat pump, or even well water. Because the radiative surface is typically a whole floor or ceiling surface, the water can be as warm as 65ºF and still provide comfort.
1 comment:
Karrick, in principle I follow your approach. The only thing I would like you to consider is the following:
If the sun is shining, you get enough direct sun to heat the shallow space you are providing. If your supplemental heat is warming up the floor before the sun is up, the floor might not be able to absorb any excess heat once the sun is hitting the floor and your space is immediately over heating. This could be remedied by reversing the flow of water thru your floor once the sun is hitting the floor and storing the excess heat in the water storage tank. This tank would need to be super insulated and be partitioned into different temperature level tanks to be able to heat and cool the space over longer time spans.
Instead of the water tank on top of the building you might be considering using the earth below as a storage tank (geo-thermal) You could expect to take about 42 to 52 degree water out of the ground and bring it up via a heat pump (en lieu of a boiler) to the necessary temperature to heat. The cooling could happen directly, just as you are proposing in your current system. Excess heat from the sun could be deposited in the ground.
I frankly don’t quite understand the PV panels on your façade. The top portion of your façade is in shadow all year. Windows in that portion of the wall have very little benefit. The amount of added shading due to the panels in the summertime is basically the amount of cantelivered structure. A slanted PV panel lower in the elevation could do more for you: The angle could be such that reflection of the PV panel could hit the upper portion of the window in the wintertime; in the summertime it would be deflected into the underside of the balcony above. If you draw a few real angles of the cantelivers, you might find an optimal placement for this panels that offer maximum exposure to natural light in the winter and maximum shading in the summer, resulting in maximum electricity production.
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