Wojciech Bujalski

Heat Accumulator in Large District Heating Systems: Simulation and Optimisation

Heat accumulators in large district heating systems are used to buffer heat production. Their main purpose is to make heat production as independent as possible from district heating system demand. To do this effectively a heat accumulator of appropriate capacity must be selected. In large district heating systems, heat accumulators can be used for equalising production over periods lasting a few hours. Accumulators can be used for optimising electricity and heat production to achieve possible highest income. It may be important in situations where on-line prices change. An optimising algorithm for heat accumulator use is shown and commented. Typical working situations are simulated and results presented.Copyright

Boosting the Efficiency of an 800 MW-Class Power Plant through Utilization of Low Temperature Heat of Flue Gases

This article presents an analysis on possible ways of utilizing low-temperature waste heat. If well-designed, this could contribute to increasing the efficiency of power plants without introducing many complex changes to the whole system. The main analysis focuses on the location of the regenerative heat exchanger in the facility. This could differ with varying temperatures of working media in the system. The base for investigations was a 800 MW-class power unit operating in off-design conditions and supplied with steam from an BB2400 boiler. Modifications to the model were made using commercially available software and by applying the Stodola equation and the SCC method. It allowed to determine the most suitable position for installing the low-temperature heat exchanger. Calculations for off-design conditions show that, after making some modifications to the system, both heat and electricity generation could be increased through the addition of a low-temperature heat exchanger.

Seasonal Thermal Energy Storage - A Size Selection

The paper presents a theoretical investigation of using a Seasonal Thermal Energy Storage facility (STES) to cover the heat demand of a complex of four buildings. The STES is placed in the ground and connected to both the local district heating network and solar panels. A number of scenarios were investigated to find an adequate size of the STES (tank size and solar panel area.) The results obtained show that the use of a STES could reduce heat consumption by 22100% depending on the architecture solution chosen.

Experimental Investigation of CO2 Separation from Lignite Flue Gases by 100 cm2 Single Molten Carbonate Fuel Cell

The paper presents an experimental investigation of using a Molten Carbonate Fuel Cell (MCFC) for reducing CO2 emission from the flue gas of a lignite boiler. The MCFC is placed in the flue gas stream and separates CO2 from the cathode side to the anode side. As a result, a mixture of CO2 and H2O is obtained; from which pure CO2 can be obtained by cryogenic condensation of water and carbon dioxide. The main advantages of this solution are: additional electricity generated, reduced CO2 emissions and higher system efficiency. The results obtained show that the use of an MCFC could reduce CO2 emissions by 90% with over 30% efficiency in additional power generation.

Experimental Investigation of CO2 Separation from Hard Coal Flue Gases by 100 cm2 Molten Carbonate Fuel Cell

The paper presents an experimental investigation of using a Molten Carbonate Fuel Cell (MCFC) for reducing CO2 emission from the flue gas of a hard coal fired boiler. The MCFC is placed in the flue gas stream and separates CO2 from the cathode side to the anode side. As a result, a mixture of CO2 and H2O is obtained; from which pure CO2 can be obtained by water condensation. The main advantages of this solution are: additional electricity generated, reduced CO2 emissions and higher system efficiency. The results obtained show that the use of an MCFC could reduce CO2 emissions by 90% with over 35% efficiency in additional power generation.

Determination of Electronic Conductance of 100 cm2 Single Molten Carbonate Fuel Cell

This work considers electronic conductance in a molten carbonate fuel cell and consequences of its existence. The voltage characteristics of cells show differences between a theoretical maximum circuit voltage and open circuit voltage (OCV). A relationship is assumed between the OCV value and electronic conductance. Based on experimental measurements an appropriate mathematical model was created. The model is used to calculate the temperature dependence of electronic conductance for the most popular types of electrolyte: Li2CO3/K2CO3. The results obtained point to the possible existence of a very close relationship between electronic conductance and open circuit voltage. This relationship enables OCV to be calculated when electronic conductance is known. Appropriate formulae can be determined. Temperature is one of the factors affecting electronic conductance. Other influencing factors do exist, but their impact on OCV is not well known. This article mentions some of them.