**5. Conclusions**

**Figure 27.** Functional scheme of the combined heat and power facility

d) CHP facility parameters

82 Sustainable Energy - Recent Studies

which is a commonly accepted lifetime with proper maintenance.

The consumers' heat demand has been carried out in the three steps:

cember and February 20% and January 25%).

4% in September up to 20% in January and April.

The time needed for the full implementation of the project is 1.5 years starting from the date of loan approval and the first disbursement (6 months for preparations, obtaining all neces‐ sary permissions and licenses, and designing; 8 months for the building the facility, and 4 months for its commissioning). The service lifetime of the CHP plant would be 25 years,

Plant parameters are determined on basis of heat demand. In this case, the analysis is com‐ plicated by different heating dynamics of the consumers (greenhouses, office building, school, hospital). The school has a different heating dynamic compared to the hospital, and all this is completely different from the dynamics of greenhouse heating system, e.g. the greenhouse needs heating at night while hospitals and schools are heated during the day.

**a.** Analysis of the heat demand in the objects where people are staying: it's been carried out on the basis of data on average monthly fuel consumption, provided by Public Company "Belgrade Plants" (October and April 5%, November 11%, March 14%, De‐

**b.** Analysis of the heat demand in the greenhouses: carried out on the basis of the heat de‐ mand, as well as the plants which are grown in the greenhouses. The data are averaged for a three-year period, and it show that average fuel consumption are varied between

**c.** Analysis of the needed active power during the heating season: In order to calculate op‐ timal power of the planned facility, the analysis of the minimal, maximal and average heat demand have been carried out for each object, as well as the overall calculation. After that, the installed thermal power of the facility can be established. The optimal solution is the one which demands minimal investment, with maximal potential gain. Analysis showed that average annual active power in the heating season is 45% of the Energy potential of renewable energy sources in the Republic of Serbia equals approximately 4.3 Mtoe/year. Biomass is deemed to be the main source of renewable energy, with estimated 2.7 Mtoe/year of energy potential, with 60% being the potential of agricultural biomass and the re‐ maining 40% being attributed to the forest biomass. Combustion of agricultural biomass was an‐ alyzed with respect to the cigar burner combustion technology, suitable for the whole-bale combustion. Technology developed was tested in the 75 kWth hot water boiler, 1 MWth demon‐ stration furnace and 1.5 MW industrial hot water boiler, where combustion of soybean and ra‐ peseed straw samples was investigated. Results obtained indicated that combustion technology developed was very convenient for combustion of biomass varieties characterized by high ash melting temperatures. A cigar firing combustion system is expected to exhibit the following ad‐ vantageous features: a) combustion of whole bales and whole energy crops; b) compact combus‐ tor design; c) short start up period, good load-following performance; d) profitable operation of smaller facilities (down to 1 MWth); e) division of combustion from the heat recovery system, usable not only for the provision of steam (for heat generation or CHP), but also as a hot gas gen‐ erator in industrial drying applications.

Cigar burner combustion system promises a more competitive use of renewable for "green" heat and power generation as well as their use in various industrial applications. In the same time, biomass combustion in cigar burners was modeled by appropriately developed numerical model. The model developed enabled the effect of fuel moisture content on the temperature distribution in the furnace to be analyzed, as well as related emissions of harm‐ ful combustion products into the environment. Research investigation conducted has dem‐ onstrated that high combustion temperatures can be achieved in furnaces used for the combustion of agricultural biomass and that achieved CO and NOx emission levels are low‐ er than the regulatory emission limit values defined by Serbian legislation.
