| Abstract [eng] |
Nowadays, increasing the low energy buildings, mostly is recommend to use for them a low temperature district heating water. The development of new buildings of higher energy efficiency class affects the existing district heating water pipeline systems which become inefficient and oversized. To solve this problem, many foreign countries have already begun to develop low temperature heat networks that could meet the needs of new consumers. One of the most relevant energy production technology for these low temperature heat networks is the seasonal accumulation of solar energy in high volume underground storage. With the increasing number of new buildings and the prospects for renewable energy development in Lithuania, the Academy, which is located in Kaunas, was selected for this final master's thesis. The innovative high volume seasonal underground storage tank was designed with integrated solar heating plant and the regenerative heat pump system, and implemented energy and economic analysis of this project. In this project was modeled 170000m3 of volume Danish type accumulation storage (PTES). On the lid of the storage tank, was designed a field of flat solar collectors in the area of 22500 m2. During the 275 days from solar energy, would be generating 9980.4 MWh of heat energy (including heat loss), which would be used to heat the storage tank water. The temperature of the return water heated from solar collectors would be 70 ºC. With “ANSYS” energy simulation program for the accumulation storage was modeled the temperature, velocity and pressure distributions in the 2D section. We calculated that without the support, the solar heating plant would not have a payback period, but with 50% of EU or APVA funds, the investment would have a payback in 10 years. The sale price of heat energy with EU funds for the installed solar heating plant on a storage tank would be: 32,02 Eur/MWh, which would allow according today's market conditions to compete with other heat producers. In this accumulation system, a regenerative industrial heat pump was used with ammonia as a working agent. This heat pump plant would ensure the energy demand between december and february - 91 days and produce 2074.8 MWh of heat energy. The sale price of energy for consumers from a heat pump plant would be 29 Eur/MWh, and the system's payback would be 9 years if 50% of the investment would be covered by EU funds. A total 12055 MWh of thermal energy would be produced per year in a seasonal accumulation storage, which would allow to provide part of the heat demand of the Academy town with developed low temperature networks. |
