DIRSIG sensitivity study

92 minimal resources to cool and heat the house as the seasons change. Employing these methods can significantly reduce energy costs. Some of these best practices and guides include:

i. Passive houses: using the sun‘s energy for heating and cooling living spaces, the building itself, or some element of it, taking advantage of the natural energy potential of materials and air that have been exposed to the sun.

ii. Superinsulation: an approach to solving thermal envelope problems through design, construction, and retrofitting. A super insulated house can include thick insulation and/or an air tight envelope.

iii. Windows and lighting: Utilization of properly designed and installed high efficiency windows and lighting.

iv. Self-sufficient homes: also known as off-grid, where the building generates and consumes its own power/energy.

v. Zero energy buildings: produce on average as much energy as they consume; designed to use zero net energy from the utility grid.

vi. Earths hips: passive solar houses built out of recycled tires and usually built into the ground.( Luis ,Ortiz. and Pout, 2008)

Maintaining thermal comfort for building occupants is one of the most important goals of HVAC design engineers. If we can understand the variables of thermal comfort in our regional climatic contexts, and the mechanisms by which they operate in relation to human physiology, then we can design buildings that provide comfort in more rich and economical ways than a standard HVAC solution. The psychrometric chart offers much insight into the integration of physiological properties, the properties of the local climate context, and other factors which allow us to design comfortable environments in a holistic manner

93 maintain the HVAC system. HVAC issues related to energy conservation play a vital role for the design of new Public buildings as well as for redesigning existing buildings.

The foremost rationale of heating ventilation and air-conditioning system is to generate a contented and healthy indoor environment, by controlling the indoor temperature, humidity level, air circulation and air quality. The prompt consideration is required on important factors like performance, efficiency, quality and morale of individuals to improve the quality of indoor environment. A well-designed HVAC system is also a crucial constituent for competent performance of buildings. The majority of the HVAC systems in utilization today were poorly designed for 34 than 60% of the energy delivered to the building is consumed by HVAC system in some countries due to the harsh climatic conditions For example HVAC systems in USA alone consume more than 25% of the total primary energy 35,-36%. As a result there is a pressing necessity for improved HVAC designs.

The energy usage due to HVAC systems represents 40% of the total energy consumed by typical office buildings. The major characteristics of HVAC equipment to determine the condition of the equipment, their operating schedule, their quality of maintenance, and their control procedures should be obtained by the energy auditor. A large number of energy efficiency measures can be considered to improve the energy performance of HVAC systems.

The majority of the HVAC systems are designed for human comfort which consists of number of fans, pumps, compressors, heat exchangers, cooling towers valves and dampers as well as a pipe and air duct assemblies of different sizes and with different operating characteristics.

Many industrial applications do have other objectives besides human comfort like to provide control of space temperature, humidity, air system will be much enhanced and more cost effective if human comfort and the demands of industry are satisfied simultaneously.

A simplified building HVAC system model was presented by Bertagnolio et al. He included simplified models of building zones and HVAC equipment. The simplified building zone model was presented on an R and C network, whose parameters were adjusted through a frequency characteristic analysis. And then it was contrasted with other detailed models, using

94 the BESTEST procedure. The study also discussed the application of the experimented model to the audit of Public buildings.

a Equipment Selection: The capacity and operating conditions for each component of the system can be determined with the help of calculations and the method of control. The selection of equipment’s can be done with the help of manufacturer's catalogs. Many equipment test codes have been written by ASHRAE, American Refrigerator Institute (ARI), Air moving and Conditioning Association (AM CA), and other societies and manufacturer groups. Comprehensive lists of these codes are mentioned in ASHRAE handbooks.

b Distribution Systems::Air ducts and piping are two kinds of HVAC distribution systems. Air ducts include supply air, return-relief air, exhaust air, and air-conveying systems.

Air ducts are used to convey air to and from desired locations. Piping is used to convey steam and condensate, heating hot water and other heat transfer fluids. Energy is required to force the fluids through these systems should be considered when systems are evaluated or compared.

c Thermal Zoning: It is a technique commonly used for greater design flexibility and energy economics in HVAC systems. In this approach a building is subdivided into a series of zones, where the set conditions can be maintained properly for a specific space and the equipment needs service only in the areas that require heating and cooling. By combining zoning with night temperature set-back controls and a time clock is an effective means of achieving occupied and unoccupied building controls. Though it is common to have many zones within one building, the number of occupied and unoccupied modes permissible in one day is normally limited to two each in any one zone, in other words the system can switch from occupied to unoccupied mode and back to occupied mode twice daily (Sekhar et al 2007). employed simulation to evaluate five most commonly used HVAC systems in Public buildings which were selected on basis of their thermal and energy performance. The results of simulation showed that the two coil induction unit had lowest consumption and performed better in providing thermal comfort, followed by VAV system with small fluctuation over the building. CA V system consumed 10% more than VAV system and at the same time gave

95 degraded performance. Hence packaged system had experiments revealed the strategies for terminal VA V system in Public building.

Research showed that use of floating supply temperature offered improved comfort conditions and energy performance. Operation stability is found when cooling effect dampers are used rather than conventional box dampers to modulate the air flow. The comfort conditions of the building have been improved when use of multiple space temperature sensors has been extended along with incorporation of lighting and HVAC.