Radiant Cooling and Heating Systems

Radiant heating or cooling is a concept that has been in practice for longer than we realise.

Archeological digs in Asia and the Aleutian islands of Alaska reveal how the inhabitants drafted smoke from fires through stone covered trenches which were excavated in the floors of their subterranean dwellings. The hot smoke heated the floor stones which then radiated into the living spaces.

An ondol, also called gudeul, in Korean traditional architecture, is underfloor heating which uses direct heat transfer from wood smoke to the underside of a thick masonry floor. The main components of the traditional ondol are a firebox or stove accessible from an adjoining (typically kitchen or master bedroom) room, a raised masonry floor underlain by horizontal smoke passages, and a vertical, freestanding chimney on the opposite exterior providing a draft. The heated floor is supported by stone piers or baffles to distribute the smoke, covered by stone slabs, clay and an impervious layer such as oiled paper.

hypocaust was an ancient Roman system of underfloor heating, used to heat houses with hot air. Hypocausts were used for heating hot baths (thermae), houses and other buildings, whether public or private. The floor was raised above the ground by pillars, called pilae stacks, with a layer of tiles, then a layer of concrete then another of tiles on top; and spaces were left inside the walls so that hot air and smoke from the furnace would pass through these enclosed areas and out of flues in the roof, thereby heating but not polluting the interior of the room.

It doesn’t surprise me that these methods were in use probably since 5000BC (if wikipedia is to be believed). Most concepts that we now follow are actually age old methods that are so logical and obvious that it is a surprise that we ignored them for so long.

A radiant cooling (or heating) system refers to a temperature-controlled surface that cools indoor temperatures by removing sensible heat and where more than half of heat transfer occurs through thermal radiation.

-ASHRAE Handbook. HVAC Systems and Equipment. Chapter 6. Panel Heating and Cooling Design. ASHRAE. 2008.

The process of radiant exchange has a negligible effect on air temperature, but through the process of convection, the air temperature will be lowered when air comes in contact with the cooled surface.

The temperature people feel is an average of the air temperature in a room and the radiant temperature from the surrounding surfaces.With radiant cooling the room temperature can be reduced which reduces the convective cooling load.

This is a surface cooling system where the water tubes are placed in the roof slab that absorbs the heat from heat sources in the room.The Slab absorbs the heat and exchanges it with the circulating water. Typically the circulating water only needs to be 2-4°C  below the desired indoor air temperature.Once having been absorbed by the actively cooled surface, heat is removed by water flowing through a hydronic circuit, replacing the warmed water with cooler water.

The heat energy is emitted from a warm element, such as a floor, wall or overhead panel, and warms people and other objects in rooms rather than directly heating the air. For radiant heating systems, you can use any one of  the three commonly applied floor heating methods: radiant air floors (air is the heat-carrying medium), electric radiant floors, and hot water (hydronic) radiant floors or use radiant panels in walls and ceilings.

For further Information:

Radiant Cooling

Sustainable Living: Part of who we are – The Hegde House, Bangalore

While I study sustainable architecture and aspire to reduce the impact of the building industry, there are families who have chosen sustainability as a way of life.

Built in 2004, the house belongs to a wonderful classmate from my undergraduate programme. What a legacy to live up to.

The bricks used for building the house are made from soil available at the site and baked through a ‘solid mud block’ process. The bricks have been made by mixing soil and stone dust and then drying it naturally under the sun for a month, saving completely on energy required to burn the bricks and transport them. 

The walls are weight bearing and only 2 concrete pillars have been erected to support a long-span beam inside.

The roofs have been made partly out of cement concrete and partly out of terracotta sandwich tiles. Air is sandwiched between the two tiles and reduces heat radiation, keeping the home naturally cool.

The central part of the house and parts of the dining area has double height and a skylight. The ventilators around the skylight draw the air from inside the house, thus providing natural ventilation. This also keeps the temperature of the house cooler by three to four degrees.

Due to the relative cool temperature in the house, the need for air-conditioners has not been felt and use of fans is minimal, thus saving electricity. “We wanted our house to be cozy and that is what we kept in mind when we asked Chitra Vishwanath of Biome to design the house for us,” says Hegde.

To view the complete article, click here.

Biogas as an Alternate Fuel

waste to biogas

 

 

The possibility of using renewable energy as a long term solution for transportation.

The possibility of recycling municipal waste and obtaining energy.

The possibility of converting Methane into a useful gas product.

Biogas typically refers to a gas produced by the breakdown of organic matter in the absence of oxygen. It is a renewable energy source, like solar and wind energy. Furthermore, biogas can be produced from regionally available raw materials such as recycled waste and is environmentally friendly.It is produced by anaerobic digestion with anaerobic bacteria or fermentation of biodegradable materials such as manure, sewage, municipal waste, green waste, plant material, and crops.

Biogas is practically produced as landfill gas (LFG) or digested gas. A biogas plant is the name often given to an anaerobic digester that treats farm wastes or energy crops. These plants can be fed with energy crops such as maize silage or biodegradable wastes including sewage sludge and food waste.During the process, an air-tight tank transforms biomass waste into methane producing renewable energy.

Eunomia (2010) analysed a range of different uses for biogas and found that using  biogas to power vehicles had the lowest carbon footprint. When the carbon impacts  of treating one tonne of organic material were analysed, the following carbon savings  could be made:

• Using biogas as a vehicle fuel has a carbon saving of 97kgCO2 equivalent.

• Using biogas for on-site has a carbon saving of 86kgCO2 equivalent.

• Pumping biogas straight to the grid has a carbon saving of 85kgCO2 equivalent.

• Using biogas to produce electricity has a carbon saving of 62kgCO2 equivalent.

Several models are already in place using biogas and working efficiently and profitably. Sweden being a leader in this area of research and development.

The presentation aims at understanding the possibility of using biogas a a replacement for fuel in Public Transport.

Further links for reading include: