RETREAT - A Cool Sustainable Habitat From TERI

Functionally an energy-efficient residential training facility for executives, RETREAT
(Resource Efficient TERI Retreat for Environmental Awareness and Training) is part of the 36-hectare Gual Pahari campus of TERI. This is located about 30km south of Delhi, in the state of Haryana. Once a degraded wasteland, it is now an epitome of green practices and sustainability. 

Incredibly, RETREAT is completely independent of external power supply sources. Standing for a powerful combination of modern science and traditional knowledge, RETREAT sets a standard in sustainability for future buildings.

Vis-à-vis conventionally designed buildings, RETREAT was constructed at an additional investment of 25% and spends 40%-50% less on energy. Less than 10 kilowatts of energy is used to light the entire complex, with the aid of specially designed skylights, energy-efficient lights, and a sophisticated system of monitoring and controlling the consumption of electricity. A conventionally designed building of the same scale would use close to 28 kilowatts to provide the same level of lighting. Moreover, the estimated CO2 saving is about 570 tonnes/year.

Design Features

Various passive design features of this complex enable reduction of space conditioning load by 10%-15%.

• The roof is insulated with vermiculite concrete topped with China mosaic for optimal heat reflection.
• Walls are insulated with 40-mm thick expanded polystyrene insulations. 
• The entire complex is south-facing, and deciduous trees all around it provide shade during summer while letting in the sun’s heat during winter by shedding their leaves.
• Part of the building is sunken into the ground in order to take advantage of ground storage and thereby stabilize internal temperature.
• East and west walls facing walls are devoid of openings and are shaded.
• Shading devices and fenestrations are designed to block the summer sun and let in the winter sun.

RETREAT makes the most of the ample solar energy acquired by the tropical nature of the country through several innovative techniques.

1. Solar Water Heaters

An array of 24 solar water heaters forms a part of the parapet of the living quarters. The system can deliver up to 2000 litres of hot water (at 65oC) every day. In winter, when the days are short and the sun less intense, a 9 kW electrical heating coil serves as a back-up source of heat.

2. Photovoltaic-Gasifier hybrid Power Plant

Photovoltaic Panels

A series of photovoltaic panels capture solar energy and store it by charging a bank of batteries. A number of panels, each measuring 1.1 by 1.2 metres, are joined and form an integral part of the roof of the building. The panels can generate up to 10.7 kilowatts peak of energy, which is fed into a 900 ampere-hour/240 volt battery bank.

Independent panels power most of the lights located outside the building. Each such light has a pair of small photovoltaic panels (roughly a metre wide and half a metre tall) and is thus a self-sufficient ‘stand-alone’ unit. A photovoltaic panel also powers the water pump.

Bio-mass Gasifier

The biomass gasifier is the main source of power during the day. Firewood, dried leaves, twigs and crop residues are used for fuelling the 50KW gasifier. This gasifier runs a generator, whose diesel requirements have been cut down to 30% after appropriate modifications.

The battery bank is thus served by two sources of power - the photovoltaic panels and the gasifier. A control device, the ‘power manager’, constantly works out the most efficient combination, deciding which is the best source at any given time. The system can function for 25–30 years; the batteries have a life of 6 years.

3. Underground Earth Tunnels

The living quarters (south block) are maintained at comfortable temperature (approximately between 20oC to 30oC) around the year by circulating naturally conditioned air using earth air tunnel system, supplemented with the system of absorption chillers powered by LPG in humid season and air-washer in dry summers.

Underground structures are not exposed to the sun and thus do not heat up as much. Secondly, the surrounding earth insulates them, which helps in maintaining a more or less constant temperature. Temperatures recorded at roughly 4 metres below the surface show that they are stable and reflect the average annual temperature of a place.

However, the cooler air underground needs to be circulated in the living space. Each room in the south block has a ‘solar chimney’. Warm air rises and escapes through the chimney, creating an air current; the cooler air from the underground tunnels to rush in to replace the warm air. Two blowers installed in the tunnels speed up the process. The same mechanism supplies warm air from the tunnel during winter.

4. Absorption Chillers

A set of eco-friendly chillers, which run on LPG and require minimum electricity, provide additional cooling when needed. As LPG is a non-renewable source of energy, efforts are under way to run the chillers on producer gas generated by the wood-based gasifiers. The conference centre, which accommodates up to 100 participants, is conditioned by means of ammonia-based absorption chillers.

5. Energy-efficient Lighting

• Energy efficient compact fluorescent lamps are used in the residential quarters, corridors, lobby and toilets.
• Energy efficient tube-lights with electronic chokes are used in conference halls, recreation rooms, computer rooms, dining hall and in administration areas.
• Glare-free daylights are provided in the conference hall, library and recreation hall through the use of specially designed skylights.

6. Waste Water Recycling – Root Zone System

In the RETREAT, waste water is recycled using the root zone techniques. In this natural technique, roots of plants with special capabilities are used to clean the water which is used for irrigation and various other purposes. It is natural waste water treatment process based on aerobic and anaerobic decomposition of the contents in the roots of the reeds and microbial organism. This system cleans (5 m3 per day) from toilets and kitchens, etc.