Long–term and Short–term Programmes for Energy Conservation in Buildings

Dr.V.V.Verma, Retired Deputy Director, Central Building Research Institute, Roorkee

In developing countries like India, the issues related to energy supply and efficiency has been brought in sharp focus during last decade. In this paper, the scope of energy conservation in buildings is discussed in details and how the short-term and long-term measures can be implemented has also been given. In addition, the pattern of energy consumption, energy utilization index of building, energy conservation measures and standards for existing buildings and new buildings with instruments for energy consumption and monitoring have been discussed here with Figures and Tables.

Introduction

The issue relating energy supply and efficiency has been discussed in front of Advisory Board of Energy for the year 2005–06 the investments required for next 15 years for measuring demand of 450 million tones of coal, 94 million tones of oil and installed capacity of 138,000mw of electricity will cost around 4,50,000 crores of rupees. Mobilizing such huge resources will be a very difficult task. Realizing the need to emphasize the management of demand, Government of India has constituted a committee of secretaries to frame policies and programmes to conserve energy in relevant sectors, viz. industrial, domestic and transport. The projected demand saving is given in Appendix 1.

Pattern of Electrical Energy Consumption

The total electrical energy production in India was around 217 Billion Kwh during 1987-88 with per capita consumption of 197 Kwh. The consumption of electricity in different sectors is:-


However in big cities, the commercial and domestic sectors, account for 30 to 40% of electric consumption which will rise with increasing trend of urbanization and industrial development.

Scope of Energy Conservation in Buildings

Now-a-days number of multistoried buildings are coming up in urban and metropolitan cities. Lot of electrical power is consumed in building sector not only in construction but also providing thermal and visual comfort, water heating etc, throughout its life cycle. Design of commercial buildings for better thermal and visual comfort with minimum consumption of energy is governed by various parameters like climate of region, orientation, thermal performance of building components and heating, cooling, and lighting requirements.

The main purpose of energy conservation measures is to reduce total power consumption during the whole year. This should be based upon pattern of energy consumption and their percentage distribution for various services. Total energy consumption is required to be predicted and compared with actual energy consumption.

Short Term and Long Term Programmes

Energy conservation in buildings can be short-term and long-term. Short term measures includes, good house keeping, modifications in operating and maintenance procedures, that requires little or no investments and can be implemented immediately.

Long term programmes can be

1. Energy auditing.
2. Building regulations and National codes.
3. Standardization of electrical applications.
4. Development of energy efficient technology.
5. Demonstration projects.
6. Training programmes and starting postgraduate level energy technology courses.
7. Government legislations and controls.
8. Electricity tariff.

Success of short term and long term programmes depending upon following measures:

1. Pattern and distribution of energy consumption.
2. Energy utilization index of the building.
3. Energy conservation measures and standards.
4. Instrumentation for monitoring energy consumption.
5. Preventive maintenance of electrical devices.

(1) Pattern of Energy Consumption

In order to determine the nature of power consumption in large multistoried office buildings, survey was made in few public and Government buildings in New Delhi. Two of these buildings are six storey having total plinth area of 50,000 sqm or so where in about 5000 employees in different categories work. The total month by consumption of electrical power in these buildings are some where– around 1.5 lakhs units (Kwh).The monthly distribution of energy consumption in two typical buildings is shown in Fig (1). It is observed from the Fig that the consumption rises approximately during summer and winter months. During summer bulk of consumption may be ascribed to the air conditioning units while during winter the bulk consumption may be attributed to heaters and radiators. As would be seen from Fig (1) the maximum power consumption during winter months of December and January shoots up to 1.8 lakhs of units per month. During the month of March and October the power consumption declines to about 0.9 lakhs units per month. This declines because heating and cooling appliances are not used during these months of moderate climate. It also been observed that during summer months the consumption is around 1.5 lakh units in a month, this rise being due to operation of air cooling and air conditioning units.

Fig (2) illustrates the hourly distribution of power consumption. The pattern is more or less of the same type as in Fig (1) but it reveals some interesting features. The average (over the year) of the power consumption is of the order of 850 Kwh/hr, for such type of buildings which employ about 5000 employees. The per capita power consumption in such type of offices can be worked out from Fig (3). Each of the employees on the average consumes 0.17 Kwh/hr. This is equivalent to 25 Kwh of power per month.

This figure of per capita power consumption is extremely low compared to that in many countries of world. The monthly distribution of power consumption by different types of services is shown in Fig (4). The services can be grouped in major categories like heating, cooling, lights and fans and other services. Except for the power consumption by essential services and lights, the other types of services will show seasonal variations as illustrated in Fig (5). These figures would clearly show that during winter, heating appliances used in building consume as much as 64% of the total power consumption in building.

It should also be noted that this power consumption by the heating units also increases the total monthly power consumption by about 80%. Almost every employee has one heater for himself. This appears to be wasteful spending of energy and therefore suggest an area where economy is possible in power consumption. Incidentally, heating and space around an individual by this type of ‘space heaters’ is not the most efficient system of winter heating. More economical devices are possible which should produce the same type of winter comfort. The winter heating load can be reduced by lowering the temperature of comfortable heating.

The summer cooling load is also in a high proportion, about 55% of the total power consumption. The demand of energy shoots up because of large number of air conditioners and air coolers that are switched on for cooling the rooms occupied by particular officials of higher ranks. Many of the officials of the lower ranks however use evaporative coolers which consumes comparatively less power than the unit air conditioners. Here also it is possible to exercise control in power consumption, firstly by raising the temperature of comfortable cooling and secondly by evaporative type of room coolers. Although during the month of April, May and June evaporative coolers produce enough comfort especially in the Northern zone of country, these are ineffective during post monsoon season. However, fans alone produce sufficient comfort during the post monsoon period, and air conditioning may not be considered essential during this period, if energy conservation is considered as the ultimate aim.

Power consumption by light and fans is not insignificant. The fans are found to consume as much as 6-10% of the total power, during pre–and post–monsoon periods. In many of the buildings it is found that distribution of fans is not scientifically based. Optimum distribution of fans and their most economical use is essential. It is observed that quite a significant amount of power, about 10-15% is consumed by lights. This is unfortunate because we are having abundant of sun light a scientific utilization of which almost eliminates use of electricity in office buildings. This aspect is covered in supplementary artificial lighting. Other services some of which are essential also consume a sizeable, proportion. These appear to be no scope of economizing in the power consumption by these services as some of which are of essential nature.

(2) Energy Utilization Index of Building

Energy utilization index is defined as total energy consumed by different devices, which require primary energy to operate that device. Primary energy may be electrical power, gas or coal. In commercial buildings in India primary energy used is mainly electrical power. This is expressed as total power consumed during a year per unit of floor area. Its unit is Kwh/sqm/year.


The energy utilization Index (E.U.I.) can be computed by energy rating of various electrical devices and their usage hours of electrical devices for different services are given in Table (1). For other services a 20% correction factor is assumed. The type of air conditioning equipment that will be most energy–efficient are also given in Table (2). This will help in selection of proper type of air conditioning plant in commercial buildings.

Method of Computation of E.U.I.

1. Work out total floor area.
2. Record total number of electrical devices and compute energy consumption from energy rating and usage time as given in Table (1).
3. Add the correction factor for other services and calculate E.U.I. after dividing this by floor area.
4. Find out total actual power consumed from monthly electrical bills and determine actual E.U.I.
5. Compare the computed and actual E.U.I.

The method is illustrated by a worked out example given below:

Compute and compare the E.U.I. for a building with floor area of 500 sq.m2 and total energy consumption for one year is 25,000 Kwh. The following electric devices are used

1. Fluorescent tubes-5 nos.
2. Ceiling fans-50 nos.
3. Unit air conditioner-1.5 ton capacity-5 nos.
4. Desert cooler-10 nos.
5. Radiators- 20 nos.

Other services used are electrical Typewriter, Photocopying machine, Water cooler and pump for water supply.

Actual E.U.I. is more than computed Energy Utilization Index. Therefore, there is scope for energy conservation measures. Even computed Energy Utilization Index can be reduced by proper implementation of thermal design standards and reducing usage hours. This can be tested in few buildings only then proper guidelines can be formulated.

Energy Conservation Measures and Standard

1. Energy Conservation Measures for Existing Buildings
   1. Providing adequate roof insulation in different climate zone of the country as per I S-3792-1978 as given in Table (3).
      
      
   2. Providing internal shading devices in all the three zones as per IS-3792-1978.
   3. Use of evaporative cooling in Hot-Dry climate as per National Building code 1983-Air conditioning and heating part viii.
   4. Heating and cooling of occupied zones rather than entire space.
   5. Thermostatic control of unit air conditioner, may be set at 30 deg c during summer and 18 deg c during winter.
   6. Replacing incandescent lamps by florescent tubes.
   7. Replacement of resistance type regulator by electronic control for fans.
   8. Photo control for energy saving in lighting.
   9. Use of solar water heater in place of geysers.
   10. Increased thermal insulation and thermostatic control of geysers
   11. Reduction of peak electricity demand.
   12. Improvement in power factor for electrical motors.
   13. Installation of time switches to close electricity system during lunch and off times.
   14. Proper maintenance of air conditioning plants and other equipment.
   15. Avoid excessive use of radiators and air conditioners.
   16. Administrative control of energy conservation and rewards for energy saving.
2. Energy Conservation Measures For New Buildings
   1. Administrative decision, if the building is to be centrally air conditioned, at the planning stage.
   2. Suitable orientation of windows mainly on equator facing side.
   3. Higher insulation of roof and exposed walls in Hot and Hot-Humid Zones.
   4. Proper design of window for day lighting and ventilation requirement.
   5. Use of adequate internal and external shading for air conditioned building.
   6. Lighting design to meet user requirement.
   7. Use of cooling day lighting tubes for supplementary artificial lighting.
   8. Provision of evaporative cooling in place of air conditioners in Hot-dry climate.
   9. Use of solar water heaters in place of geysers.
   10. Temperature controls and photo control for energy saving in heating/cooling and lighting,
   11. Efficient design and maintenance of heating, cooling and lighting system.
3. Instruments for Energy Consumption; Monitoring
   The basic purpose of instruments and instruments used for monitoring energy consumption are:
   1. Recording of total power consumption - - - Watt hour meter.
   2. Recording of power demand and recording of power factor - - - Power factor meter.
   3. Checking comfort conditions - - - Dry and wet bulb physcometer.
   4. Checking lighting levels - - -Luxmeter
   5. Recording of percentage running time - - - Time totalize, Air velocity meters, Time switches.
   6. Checking performance of heating and

Cooling units - - - Temperature measuring and recording Instruments, Thermocouples and Resistance thermometers.

The instruments are available in different rating and depending upon size and type of buildings, these instruments can be selected.

Constraints

Certain constraints have been noticed while implementing short and long term programmes by various agencies.

1. Users are not very serious about energy conservation due to lack of awareness and benefits which acquired by saving energy.
2. Often they encounter administrative delays as well as lack of sufficient fund and manpower to implement even simple house keeping measures.
3. For measures programmes which need large capital investments, it is difficult to justify these investments for buildings which do not operate a commercial basis.
4. Some energy conservation measures which gives better comfort and working conditions involving sufficient capital out lays attract very lower priority from the Government, financial institutions and commercial establishments.

References

• Report on Energy Conservation in Buildings-Phase,I,IIA and IIB (1979),Submitted to Ministry of Energy, Govt. of India.
• National Building Code of India, 1983-Group IV Part VIII-Building Services.
• Building Control Division (1980)- Handbook on energy conservation in buildings and building services, Building Control Division-Public Works Department of Ministry of National Development, Singapore.
• Handbook on functional requirements of buildings published by I.S.I., New Delhi.
• Recommendations of National Seminar on ENERGY Conservations in Buildings Organized by NPC at New Delhi on 01 Sept,’89.