The Study Of Solar Chimney Energy Saving Potential

Solar chimney is a low-carbon,energy-saving passive technology that uses solar energy to enhance natural ventilation.The world has seen its increasing application in buildings.However,there is few report on the energy-saving potential of solar chimney.This thesis aims to find out the energy saving potential of the solar chimney as a means to enhance natural ventilation through modeling study using lab tests and field tests and energy simulation studies.Results of energy simulation in various climate zones in China are reported.Firstly,lab tests were conducted using electric heating panel to represent solar heating.The effects of entrance configuration and size affects were studied.Results show that there is a match between the chimney size and the entrance size.A small size of entrance could limit the chimney ventilation rate.When the inlet size is close to the size of the chimney channel,the effect of pipe on ventilation rates diminished.A inlet size larger than the chimney channel does not seem to help the flow rate increase.Then,fields experiments were conducted on a solar chimney installed on a residential building model.Data from several weeks of measurements show that the solar chimney ventilation rate is not only satisfying during the daytime with sufficient solar radiation but also satisfying during rainy days or nighttime.In the later case,the indoor temperature is higher than the outdoor temperature,which is referred as‘inverse conditions'to distinct it from the normal conditions when the solar radiation causes highest temperature in the chimney channel.Because of the prevailing 'inverse conditions',the ventilation rate during the field tests were higher than 1 ach for most of the time.However,the existing solar chimney model implemented in the energy simulation tool EnergyPlus fails to account for 'inverse conditions' and thus cannot be used directly to simulation solar chimney.Based on the experiment data,the thesis revised the existing soalr chimney model to account for the indoor temperature,chimney outlet temperature,and outdoor temperature.The revised model will be the first one that can be used to simulate the annual performance of the solar chimney buildings.Furthermore,the corresponding codes were revised as well in the EnergyPlus to reflect the new model and the new control of the building ventilation strategy.Thus,simulation of annual performance of the solar chimney becomes possible for the first time.Last,a low energy residential model was used to investigate the annul energy performance of solar chimney in 7 major climates in China.Energy saving potential was evaluated by compar-ing the energy consumptions between the building with solar chimney and the one without.The study found that the application of solar chimneys in buildings can effectively save energy with a reasonable control of solar chimney flow.The solar chimney energy saves energy in two aspects:1)replacing the need of mechanical ventilation,2)increased passive heating and cooling.Reulsts show that the presence of solar chimney can reduce 60-90%of the mechanical ventilation energy.In colder regions,due to the 'inverse condition',indoor temperature driven chimney flow prevails and the mechanical fan energy could be reduced by 90%.The reduction rate is higher than those in the warmer or hotter areas.The total HVAC energy savings of solar chimneys in various regions is between 156.8 and 727.6 kWh.Among them,the hot summer and cold winter regions have more energy saving potential perhaps due to its four distinct seasons.There is greater potential in passive heating and passive cooling by solar chimney.In hot areas,e.g.Guangzhou,due to its high cooling load,most of the chimney ventilation comes from solar radiation.Therefore,the potential energy saving amount is lower than in the other cities.It can be concluded that the solar chimney is capable of providing considerable amount of ventilation flow throughout the year,driven by both the solar energy and the indoor heating sources.The studied building is small in size and has a small demand of ventilation.A larger building will have a larger demand and more energy saving with hardly any operation cost.