Cooling load forecasting-based predictive optimisation for chiller plants

Extensive electric power is required to maintain indoor thermal comfort using heating, ventilation and air conditioning (HVAC) systems, of which, water-cooled chiller plants consume more than 50% of the total electric power. To improve energy efficiency, supervisory optimisation control can be adopted. The controlled variables are usually optimised according to instant building cooling load and ambient wet bulb air temperature at regular time intervals. In this way, the energy efficiency of chiller plants has been improved. However, with an inherent assumption that the instant building cooling load and ambient wet bulb temperature remain constant in the coming time interval, the energy efficiency potential has not been fully realised, especially when cooling loads vary suddenly and extremely. To solve this problem, a cooling load forecasting-based predictive optimisation method is proposed. Instead of minimising the instant system power according to the instant building cooling load and ambient wet bulb temperature, the controlled variables are derived to minimise the sum of the instant system power and one-time-step-ahead future system power according to both instant and forecasted future building cooling loads. With this method, the energy efficiency potential of a chiller plant can be further improved without shortening the operation time interval. 80% redundant energy consumption has been reduced for the sample chiller plant; energy can be saved for chiller plants that work for years. The evaluation on the effect of cooling load forecasting accuracy turns out that the more accurate the forecasts are, the more redundant energy consumption can be reduced

Tests of a reduced-scale experimental model of a building solar heating-cooling system

An experimental solar heating and cooling system model has been built and operated, combining elements that are programmable (e.g., heating and cooling load of a building and collected solar energy) with experimental equipment. The experimental system model was based on the loads and components used in the Solar Building Test Facility (SBTF), which includes a 1394 sq m solar collector field at NASA Langley. These tests covered 5 continuous days under summer conditions. For the system model up to 55 percent of the simulated collected solar energy was used for the building load. This amount of solar energy supplied 35 percent of the building cooling load. Heat loss was significant. If tank heat loss were eliminated, which would make it similar to the actual SBTF, 75 percent of the collected solar energy would be used. This amount would supply approximately 50 percent of the building cooling load. A higher fraction of solar energy is possible with a more performance-optimized system

A Control Scheme of Enhanced Reliability for Multiple Chiller Plants Using Mergerd Building Cooling Load Measurements

This paper presents a control scheme which utilizes the enhanced instantaneous cooling load measurements to improve the reliability of chiller sequencing control. The enhanced measurement is obtained by merging two different measurements of building cooling load using data fusion technique. One is the direct cooling load measurement, which is obtained directly using the differential water temperature and water flow rate measurements. The other is the indirect cooling load measurement, which estimates the cooling load using chiller models based on the instantaneous chiller electrical power input and condition measured variables. The control performance of the proposed scheme is validated in this paper

Load calculations of radiant cooling systems for sizing the plant

AbstractThe aim of this study was, by using a building simulation software, to prove that a radiant cooling system should not be sized based on the maximum cooling load but at a lower value. For that reason six radiant cooling models were simulated with two control principles using 100%, 70% and 50% of the maximum cooling load. It was concluded that all tested systems were able to provide an acceptable thermal environment even when the 50% of the maximum cooling load was used. From all the simulated systems the one that performed the best under both control principles was the ESCS ceiling system. Finally it was proved that ventilation systems should be sized based on the maximum cooling load

The effect of building form on cooling load in hot and humid climate

High energy consumption correspondingly starts from an inefficient use of energy. The communities are increasingly concerned towards a better usage of energy for more comfortable life in future. Since past decades the standard of living has improved, people tend to expect a better comfort level which they consider the usage of air conditioning system is a must. The design of a building is required to provide comfort and efficient energy usage. The research objectives are to study the concept and influence of building form and geometry, investigate the cooling load in building space and to explore building form strategies in decreasing the cooling load. The research investigates the development and relationship of basic geometrical building form in lowering cooling load of a medium five-storey building. The manifestation of different thermal behaviour of each basic form was based on different volume, height and surface. The study manipulates the variables in three steps. The first step is the exploration and understanding of basic forms having the same height level, volume and different surface. The second step is investigating further on basic form by having different height levels but same overall volume. The final step explores the same volume, height level and surface area of the geometric forms. The study was conducted using computer simulation analysis program Autodesk Ecotect 2011. The outcome of the research reveals that compact shape and lower ratios of surface to volume result in lower cooling loads. The building with a different floor height but same overall volume shows the effect of lowering the cooling load. The increase number of floor zones will give lower cooling load. Experimentation of the basic forms reveals that an exposed surface area plays a huge role in lowering cooling load. Compact arrangement of spaces in a building also gives impact towards cooling load. The result of simulation model analysis shows the orientation aspect is less significant with 0.5 to 0.6 % difference towards lowering the cooling load compared to the exposed surface area of the form that shows 5 up to 19 % difference of cooling load from each geometry form. This research is significant in helping to accumulate the information regarding building form behaviour. Based on the result, the manipulation of exposed surface of the basic building form will reduce the cooling load

Impact of urban geometry on indoor air temperature and cooling energy consumption in traditional and formal urban environments

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the URI link.This study explores the effect of outdoor microclimatic environment on indoor conditions in a tropical warm-humid climate. An indoor air temperature and building energy performance analysis is carried out for the real case-study areas to examine the impact of urban geometry on building indoor conditions. The study incorporates microclimatic data from CFD, micro-climatic tool ENVI-met into building energy performance analysis using IES-VE. Findings reveal that diversity in urban geometry in deep urban canyons is helpful in reducing the indoor air temperature and cooling load. On average, cooling load in model rooms in the formal area is 21% higher for 1st floors (40% for top floors) compared to the corresponding rooms in the traditional area. In terms of solar gains, the difference was 30% for the 1st floors and 91% for the top floors, with rooms in the formal area having the higher ranges. Furthermore, the room air temperature in the traditional area was found to be 0.6-1.6 Deg C lower than those in the formal area

Portable Thermoelectric Cooler Box Performance with Variation of Input Power and Cooling Load

The thermoelectric module is a device that works by using the Peltier effect when electrical power supplied on it. In this study, the thermoelectric module is applied as thermoelectric cooler (TEC) using air cooling heat sink where cooling box capacity is 22 L. This paper experimentally investigates the thermal performance of thermoelectric cooler with a variation on input power and cooling load. The investigation has been conducted by three variations on input power (50.5W, 72.72W and 113.64W) and by two variations of the cooling load using mineral water (1440 mL and 2880 mL) with input power 113.64W. The box temperature achieved at input power 50.5W, 72.72W and 113.64W are 19.98oC, 19.77oC and 18.52oC, respectively. While at the cooling load of 1440 mL and 2880 mL, the temperature achieved in the box are 22.45oC and 23.32oC, respectively. The test results showed that in variation on the input power from low to high, the temperature in box becomes lower on high input power and causes the lower of COP, this is because more energy could be absorbed on high input power. In the cooling load variation, the greater the cooling load given in cooling box, then the longer the box  temperature  stability can be achieved because of more energy needed for decreasing the temperature of cooling box