Changes for cold and heat source supporting system of Education Bureau
变更原因：Reasons for Change
1. According to the original scheme, the newly increased heat -source tower of the Education Bureau′s building will be located in outdoor terrace of ground first floor, close to northwest outer wall of office building. Wuhan Municipal Education Bureau reflects that if the equipment of energy tower is installed in outdoor terrace of the first floor, it will block the fire fighting access of Education Bureau′s building at variance with building design fire protection rules, and the noise caused by the equipment could affect normal work of neighboring office. Therefore, Wuhan Municipal Education Bureau suggests that according to architectural structure condition of the building, without adding load-bearing of the building, remove the old energy tower on the roof, and place the new energy tower in the location of the old tower.
2. In the original scheme, the heat pump system of the heat-source tower adopts the methods of detecting the solubility of salt solution by hand, according to the detection value, adjusts the solubility of salt solution with hand feeding (antifreeze agent) within the scope of the allowable value, and makes the heat pump system of hear-source tower operate stably in the conditions of high energy efficiency ration. Using this model, if manual detection and feeding appears deviation, at best, the COP of heat pump system in the heat-source tower will be reduced, the fractional energy savings will be lowered and the pay back period will be extended; at worst, the rising freezing point resulted from low solubility of salt solution may cause the solution to freeze under the low temperature, and lead to damage to the evaporator pipelines of the heat pump units in heat-source tower, the units will shut down.
The heat-source tower uses the water as the carrier when refrigerating in summer, and uses salt solution (water +antifreeze agent )as the carrier when heating in winter, in original scheme , the wastage of antifreeze agent producing during the normal operation of the heat pump units of heat-source tower and the recycling use of salt solution are not taken into account. The annual consumption expense of antifreeze agent is 42,300.00 RMB.
In the original scheme and energy audit report, the calculation method as 44.21% ratio of saving and 7.96-year payback period neither considered the annual consumption expense of antifreeze agent. If consider this expense, the actual ratio of saving should be 38.71%, and the actual payback period should be 9.11 years.
Now adding an equipment for solubility testing, self-feeding and saline solution payback, the project cost of which is 198,300.00 RMB. But because of the additional equipment, the annual consumption expense of antifreeze agent will reduce 17,415.00 RMB, ratio of saving will rise to 40.97%, and payback period reduce to 8.77 years. Both of the ratio of saving and payback period are superior to the original scheme.
变更过程：Processes for change
The project cost produced by the changes of the adjustment of heat-source tower location and the equipment for solubility testing, self-feeding and saline solution payback reaches 376,118.99 RMB, which exceeds NDRC approved estimates. However, the location of heat-source tower must be adjusted, while the equipment for solubility testing, self-feeding and saline solution payback can ensure the heat-source tower pump assembly running stably. In order to improve the ratio of saving and shorten the payback period, both the 2 changes should be implemented. By deeply analyzing all the energy-saving measures in contract, combining the education bureau′s site investigation, my company decides to reduce the reconstruction of building external windows(93,000RMB), the reconstruction of fan-coil units system(72,000RMB), the reconstruction of cooling-water pump(24,000RMB), electric control valves and reduce the work of frequency converters in transducer control cabin(40,000RMB) and complete above-mentioned 2 changes with contract tentative amount. Because the loss of ratio of saving by the reconstruction of building external windows and fan-coil units system is offset by the improvement of ratio of saving by the above-mentioned 2 changes, as well as the contract price of education bureau energy-saving reconstruction is unadjusted, the ratio of saving and payback period remain unchanged, as 38.7% ratio of saving and 9.11-year payback period.
On March 24,2000, according to “Project Engineering Change Management Method ”, Wuhan Municipal Building Energy Efficiency Office hosted technology discussion meeting about installation position adjustment of energy tower and supporting system optimization of cold and heat source of the building of Wuhan Municipal Education Bureau, after full discussion, the meeting agreed to move the installation position of energy tower form the ground to the roof, improve corresponding cooling water system design; agreed with supporting system optimization design of cold and heat source; agreed to simply outer window reconstruction scheme , use the scheme of adding manual control valves in each layer to replace the modification scheme of original fan coil control system , use the original cooling pump instead of two cooling water pumps, and use two frequency converters instead of original four frequency converters .