-The aim of the study is to determine whether and to what extent it is possible to use excess electricity produced by wind power plants during low demand periods for district heat production by heat pumps. Energy system analysis on an hourly basis is conducted at various capacities of wind power plants. The results show that it is possible to increase the share of renewable energy sources, decrease the use of primary energy sources and CO 2 emissions per unit of the produced energy, i.e. heat and electricity, by using the surplus electricity produced by wind power in the heat pumps combined with the heat storage.

In a well-functioning and sustainable national energy sector, each of its elements should function with maximum efficiency. To ensure maximum efficiency and study possible improvement of the sector, a scaling-up framework is presented in this work. The scaling-up framework means that the starting point is a CHP unit and its operation, the next step of aggregation is in a district heating network, followed by a municipal energy plan and finally leading to a low carbon strategy. In this framework the authors argue, that the successful, innovative practices developed and tested at the lower level of aggregation can be then transferred to the upper levels of aggregation, thus leading to a scaling-up effect of innovative practices. The work summarizes 12 methodologies used in the energy sector, by dividing these methodologies among the levels of aggregation in a scaling-up framework.Environmental and Climate Technologies ____________________________________________________________________________ 2015 / 15 6 electricity can be held together, but also because fuel savings can be achieved and therefore more an efficient overall conversion process is possible.Çakir et al. [9] estimate that fuel savings via a cogeneration regime can reach 50 %. Since CHP plants and biofuel production require the same feedstock, Leduc et al. [10] investigated whether the use of biomass should be supported in the EU. The results showed that the CHP plants are preferred over biofuel production plants in cases when carbon costs more than 50 EUR per tCO2 and the support for biofuel is below 10 EUR per GJ. Moreover, the highest potential for both biofuel and CHP was found in the countries around the Baltic Sea, Austria, Czech Republic, Hungary and Poland. The sustainable development of biomass CHP plants in Latvia was studied by Cimdina et al. [11].Nevertheless the installation of CHP and the conversion of energy production units to renewables are not enough. In sustainable energy production systems, the analysis of operational performance is vital. The literature review traces a wide range of factors affecting the performance of the cogeneration power plant. Cimdina et al. [12] determines the essential factors of the operation performance in biomass cogeneration power by presenting quantitative equations.Biomass CHP can be assessed using various indicators such as efficiency [13], primary energy savings [14], emergy efficiency [10], internal rate of return (IRR) and net present value (NPV) [15], as well as the costs of heat and power production [16]. Nevertheless, traditionally applied assessment methods of energy and mass flows and economic analysis do not provide an integral assessment. In this case another methodology should be applied. Emergy and exergy analysis could serve as such an integral assessment method [17].Exergy is defined as the maximal useful work obtained from a system while the system interacts with environment. Nowadays energy and exergy analyses are done for power plants [18] and for various energy technologies, such as i...

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The role of power and thermal energy is impossible to overestimate in development of both state economy sector and everyday life of households. Importance is connected with use of resources, economical feasibility and effect to climate changes. The optimization of energy production allows to promote development of sustainable society. The most popular and efficient technologies for generation of power and thermal energy are cogeneration plants (CHP). Traditional evaluation methodologies of energy production systems are based on analysis of energy and mass balances as well as on cost analysis. It is not enough for assessment of complete sustainability of system. Necessary environmental impact assessment of energy production is possible to implement by use of emergy analysis. Definition of emergy includes one type of energy, which is used directly or indirectly to produce materials, provide services and finances. Emergy dimension is emjoules (seJ.). Paper presents case study of emergy analysis of different operation modes of one cogeneration plant.

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