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Renewable Energy in Buildings

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Buildings account for about one-third of the energy consumed. Heating and cooling systems use 60% of this energy, while lights and appliances use another 40%. Manufacturing and transporting building materials require additional energy. By carefully applying renewable energy practices, energy use in buildings can be reduced dramatically and strengthen the economy by reducing the need for fossil fuels and nuclear energy.

The solar passive architectural design involves the use of a building’s structure to capture sunlight and store heat that can alone, save up to 50% or more of energy used. The use of landscaping, natural breezes and the choice of building materials in these buildings further add to its energy efficiency. The active system used either in conjunction with a passive design or as a stand-alone cooling or heating system involves moving parts that circulate air through a building or move a liquid, most often water. These systems may also be combined with thermal storage to further increase energy savings and comfort.

Daylighting, or the use of natural light in a building is one of the most rewarding design measures and is consistent with the heating and cooling aspects of passive design. Placing light coloured reflective surfaces close to windows will allow light to bounce farther into the room. Shades and blinds always enhance the ability to control the light. A carefully controlled daylight can provide all of the necessary interior lighting with less heat emitted to the interior spaces reducing HVAC loads. Open interior plans that enable natural light to penetrate to all parts of the structure, therefore, are especially important in commercial buildings, where electric lights are in the highest demands.

Today’s water heating technology is far superior to the solar water heaters of the 1970s and utility incentives for solar water heating are on the increase. The payback period for the heaters depend on the system, climatic conditions, and the local utility incentives. Possible future use of the roof for photovoltaic and solar water heaters represents the rationale for orienting roofs to the south.

Energy Considerations

Any land-use development should maximize public transportation possibilities by placing mixed types of housing in close proximity to businesses and commercial operations. Thoughtful planning can protect the natural environment and the community character by reducing the need for roadway expansion, and thereby decreasing the air pollutant emissions and conserving our limited energy resources.

Any development of buildings places an extra demand on local utilities. The natural resources that are affected, therefore, must be considered in planning, not just at the current costs, but at the costs the development will place on the community throughout its life.

The construction of new buildings requires energy, and the building materials themselves embody energy. These materials have to be dug out of the ground, cut from the forest or field, or created by human technology. All these processes use energy. The distance that materials must be transported, and the intensive energy needed to prepare them for use in buildings, should be considered when choosing a material.

The Cost of Energy-efficient construction

Many of the energy-efficient design features produce only very small cost increases and they can make good financial sense for building buyers. By spending more money on the construction of the building, on good windows and on more insulation – energy bills will be smaller, in the long term, the life cycle costs will decrease and the building will be more affordable to own. Thus, every purchase should be evaluated in terms of multiyear energy cost savings.

Energy-efficient buildings enable the banks and the builder to make money through the higher cost of construction and the owner will save money through the decreased operation costs. While higher construction costs of renewable systems might result in larger mortgage payments, the increased efficiency will result in lower energy bills and the two can balance each other out.

Cost of buying durable, recyclable or reusable construction materials up-front is more but more cost effective than buying a less-expensive and less-durable product. If something will last 50 years rather than 10 years, the payback is attractive in a lifecycle cost analysis and it will certainly place less demand on the amount of waste we create as society.

Case Study:

IIT Kanpur – Solar passive

The campus has an air-conditioned area of 1912sqm and a non-air-conditioned area of 2328sqm. This campus falls in the composite climatic zone, predominantly requiring cooling and heating in summer and winter respectively to maintain thermal comfort for the occupants.

Design of an earth air tunnel using the geothermal property of the earth has resulted in a reduction of more than 15% of the building cooling load. Efficient condenser cooling through an on-site water body and use of thermal energy storage has increased the efficiency and reliability of the air conditioning system.

Building design and envelope was optimised through selection of appropriate wall and roof construction and through adoption of solar passive methods to provide shading devices for windows and roof, which would reduce energy demand to condition the spaces. The high performance glass for windows, while allowing light inside, does not allow heat and also keeps office cool from inside during the day, decreasing the load on HVAC systems.

As a result there is a 47% reduction in energy consumption and 65% reduction in water consumption as compared to GRIHA benchmarks. This a 5-star GRIHA rated building.

Case Study:

Infosys, Pocharam – Radiant Cooling

Infosys, Pocharam is the first commercial radiant cooled building in India. The system which is 30-40% more efficient than the conventional air-conditioning systems has achieved 56% reduction in energy consumption and 56% reduction in water consumption as compared to GRIHA benchmarks. In a conventional air-conditioning system, air circulates in the room or premises to the cool surroundings. But when compared to air, water is more efficient in carrying energy that the same volume of air can carry. This property of water is used to in a radiant cooling system where cold water flows through pipes embedded in the slab and cools the entire slab. Cooling inside the office space is achieved when the cold slab absorbs the heat (radiation) generated by people, computers, lighting and other equipment which are exposed to the slab.

Fresh air is supplied through an air system to maintain a healthy indoor environment, and also to control the moisture inside the office space. The latent heat load (heat generated through release of water vapour like the one generated while we breathe out) is removed through this Dedicated Outdoor Air System (DOAS). The radiant cooling offers healthier indoor air quality as there is no recirculation of air in the system. This technology also reduces the temperature of the slab improving the comfort of the occupants.

Case Study:

Suzlon, One Earth, Pune- Renewable Energy

Suzlon One Earth is a 100% renewable energy campus with both on- and off-site renewable energy, that includes solar and wind. Out of this, 7% of the total energy consumption comes from 18 on-site hybrid wind turbines, solar panels and photovoltaic cells and 93% of the remaining is from off-site wind turbines. This building has 154.83kW renewable energy incorporated and 100% of the outdoor lighting and the communication server are run on renewable energy resources.

The orientations of the blocks are such that the majority of building facades face North, South, North-west and South-East. This enables adequate day lighting and glare control. Glazing on the first and second floors has been shaded from direct solar radiation using louvers. High efficiency mechanical systems integrated with the efficient building envelope ensure that the energy consumption of the building is reduced significantly.

The HVAC scheme is designed innovatively combining various energy efficient components like pre-cooling of fresh air, heat recovery/exchange mechanisms to minimise overall energy consumption.

Photovoltaic systems and micro wind turbines are integrated in the design. In totality, Suzlon One Earth managed to reduce its energy consumption by 47.2%, below the bench marked energy consumption by GRIHA. This project has achieved a 5-star GRIHA rating.

 

 

Courtesy: GRIHA Council, Sustainable Habitat Division,
TERI (The Energy and Resources Institute)

 

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