Spatial distribution of emissions, temperatures, and particulate matter in a combustion zone of a pellet boiler

Photovoltaic (PV) micro-installations producing renewable electricity and automatic pellet boilers producing renewable heat energy are promising solutions for single-family houses. A single-family house equipped with a prosumer 7.56 kWp PV micro-installation and a 26 kW pellet boiler was analyzed. This study aimed to analyze the production and use of electricity and heat over three successive years (from 1 January 2021 to 31 December 2023) and to identify opportunities for securing renewable energy supply for the house. Electricity production by the PV was, on average, 6481 kWh year−1; the amount of energy fed into the grid was 4907 kWh year−1; and the electricity consumption by the house was 4606 kWh year−1. The electricity supply for the house was secured by drawing an average of 34.2% of energy directly from the PV and 85.2% from the grid. Based on mathematical modeling, it was determined that if the PV installation had been located to the south (azimuth 180°) in the analyzed period, the maximum average production would have been 6897 kWh. Total annual heat and electricity consumption by the house over three years amounted, on average, to 39,059 kWh year−1. Heat energy accounted for a dominant proportion of 88.2%. From a year-round perspective, a properly selected small multi-energy installation can ensure energy self-sufficiency and provide renewable energy to a single-family house.

Air quality protection and emission reduction are essential for ensuring a high quality of life and public health. This study evaluates the influence of fuel dosage on the performance of an automatic pellet boiler, focusing on heat output, gaseous emissions (carbon monoxide, nitrogen and sulfur oxides), particulate matter and the efficiency of an electrostatic precipitator. Fuel dosage was adjusted through supply/standstill ratios in seconds (11/15, 14/20, 18/25, 22/30, 25/35), and a four-tube precipitator was designed, increasing the collection surface area by 1.6 times and improving particle separation efficiency. Results showed that fuel dosage did not impact heat output or nitrogen oxides. Carbon monoxide slightly increased as the fuel dosage interval widened without the precipitator but decreased marginally when the precipitator was operational. However, the use of the electrostatic precipitator did not have a significant impact on carbon monoxide, these values differed only very slightly. Particulate matter at 10% oxygen increased from 18.83mg∙m⁻3 (11/15) to 26.82mg∙m⁻3 (22/30) without the precipitator and decreased significantly with the optimized precipitator, achieving a maximum collection efficiency of 90.27% (18/25). Regression models developed for particulate matter concentrations and separation efficiency demonstrated strong predictive accuracy, with coefficient of determination values of 0.946 and 0.694, respectively.

Integration of a Stirling engine in a biomass boiler can be an interesting renewable alternative for the supply of heat and electricity in isolated homes located in areas where local biomass is available and during months when sunlight is low. Since this integration requires a careful coupling of the engine and boiler, an integrated model of these two devices is a relevant issue. In this case, a modular integrated model of a 25 kWth biomass pellet boiler, fire-tube with a cylindrical water jacket, coupled to a 1 kWe free piston Stirling engine is presented. To model the boiler, and take into account the location of the Stirling head, the zonal method was chosen, which allows estimating this temperature from an additional set of surrounding temperatures. For the Stirling engin, a model widely used to evaluate those engines was used. Various software tools have been used to integrate the model sequentially. The integrated model predicts the thermal and electrical production based on different opera-tion parameters, such as the boiler load in 5% fractions of its load from 50 to 100%. The obtained results, which will be validated with the experimental setup, show a maximum output of approximately 600 W for the engine and a decreasing tem-perature profile in the combustion chamber, as a function of the partial load.

Estimation of emission factors from residential Ecodesign boilers considering characteristic phases of their operation.

Modern low-power boilers with automatic burners require electricity for proper operation. The electricity voltage in the network is not constant and is subject to fluctuations. Variations in voltage will have the most significant impact on the operation of electric motors since their speed is controlled by changing the voltage. The purpose of this research was to assess the impact of supply voltage deviations within the range allowed by the EN 60038:2012 standard (230 V ±10%, i.e., 207 V and 253 V) on boiler operation. This study analysed the effects of these variations on flue gas and dust emissions during boiler operation at full load, as well as on the boiler firing process. Tests were conducted on a boiler with a nominal output of 25 kW. Changes in voltage significantly influenced the blower fan speed. For the nominal boiler output, at 253 V the speed increased by 17.6%, and at 207 V it decreased by 20.4%. Variations in voltage affected the volume of air supplied to the combustion chamber, altering the excess air ratio (λ): 1.8 at 230 V, 2.1 at a higher voltage, and 1.4 at a lower voltage. Changes in voltage translated into changes in exhaust gas temperature and flue gas and dust emissions. Boiler operation at 253 V increased CO emissions by 77.2%, NOx by 31.2%, and dust by 12.5%. In contrast, at 207 V, emissions were lower, with CO decreasing by 17.3%, NOx by 11.7%, and dust by 18.8%. Fluctuations in voltage further influenced the boiler’s ignition time; the ignition process was four times longer at a higher voltage and twice as long at a lower voltage. The results of these studies underscore the necessity of adapting boiler designs to fluctuating voltage conditions.

This paper is an analysis which provides an objective perspective on the performance of different heating sources to facilitate informed decisions regarding investments in thermal energy production equipment that have a low impact on the environment. The aim of the study is to investigate different possibilities to reduce the power consumption and environmental impact taking account annual electricity consumption building for the central-western location in Romania. This paper presented the technical-cost benefit and environmental impact analysis of three alternative heating systems versus conventional systems with natural gas boiler. The obtained results show the higher cost is for ground-to-water heat pump solution and for pellet boiler the price initial investment is higher than that of a gas boiler with 2.15% but is like that of an air-to-water or ground-to-water heat pump. The total operating cost for pellet boiler, air-to-water heat pump and ground-to-water heat pump is higher than natural gas boiler with 65%, 23%, respectively 10%. The amount of CO2 emitted into the atmosphere decreases significantly with solutions air-to-water heat pump and ground-to-water heat pump, with the minimum value of 2502 kg CO2 obtained for the last.

The promotion of Renewable Energy Sources RES installations in single-family houses is an element of the broadly understood decarbonisation strategy. Investments in photovoltaic installations and pellet boilers have a direct effect on decreasing CO2 emissions, thereby contributing to the improvement in air quality and mitigation of climate change, but the question remains of whether they are economically viable. High energy consumption by households results in a significant burden on their budgets. The purpose of this study was to conduct an economic analysis of the renewable electricity (photovoltaic microinstallation—PV) and heat (a pellet boiler) produced in three consecutive years by a single family situated in North-Eastern Poland. The economic analysis was based on the determination of the electricity and heat production costs for renewable energy sources and selected fossil fuels. Profitability metrics such as net present value, internal rate of return and discounted payback period were used for the assessment. For the comparison of electricity costs, the costs of electricity from the power grid were confronted with the costs of electricity generation from a PV microinstallation. For the comparison of heat production costs, the following scenarios were analysed: (i) eco-pea coal vs. pellet, (ii) natural gas vs. pellet and (iii) heating oil vs. pellet. Next, comparisons were made and analysed for multi-energy systems. When comparing the PV microinstallation investment with the variant of using electricity from the power grid, a positive NPV equal to EUR 5959 was obtained for the former, which proved it was profitable. Among the heat generation variants, the lowest total costs were related to eco-pea coal (EUR 29,527), followed by pellet (EUR 33,151) and then natural gas (EUR 39,802), while the highest costs of heat generation were attributed to burning heating oil (EUR 63,445), being nearly twice as high as the cost of burning pellets. This analysis of multi-energy systems showed that the RES system composed of a PV microinstallation for electricity production and a pellet-fired boiler for heat generation was most advantageous because it yielded the lowest total costs (EUR 41,265) among all the analysed variants. A properly selected PV microinstallation and an automatic pellet-fired boiler can make a single-family house economical and provide it with sufficient amounts of renewable electric and heat power throughout the year.

Use of wood pellets is continuously increasing in Europe, and most of them carry the ENplus A1 label. In this research, 28 assortments of such A1-labeled wood pellets were collected from the fuel market and were comprehensively analyzed and combusted in two residential pellet stoves; up to 8 pellet assortments were also combusted in two residential pellet boilers. Correlation analyses have been carried out, including the results from 31 additional pellet assortments from an own pelleting process where specifically tailored pellet characteristics were produced using different wood species. In particular, the effects of pellet length, moisture content, fines content, raw material preparation, additives, and wood species were investigated to identify the dependencies between the investigated fuel parameters and pollutant emissions. The most important parameters influencing pollutant emissions especially from domestic pellet stoves were identified as the potassium content of the fuel, the hardwood content, the carbonate content of the fuel ash, the Si/K molar ratio, and the energy density. Total particulate matter (TPM) emissions ranged from 45 to 246 mg/m3 for pellet stove 1, whereas for pellet stove 2, TPM emissions from 23 to 58 mg/m3 have been observed. Not the same pellets performed best or worst in both pellet stoves. Overall, the current state of the art stoves showed a greater response to variations in pellet quality compared with boilers, and improvements in pellet stove technology and control are recommended.

Environmental, economic, and eco-efficiency assessment of residential heating systems for low-rise buildings

Torrefied and pyrolyzed pellets and their environmental impact in household heating

Prediction of particulate matter during the combustion of wood pellets with the addition of face mask waste

Estimation of wood biomass boiler use in cold climate regions on CO2 emissions of light-frame timber structure

Energy usage of spruce with waste face masks and spent coffee grounds as fuel in a pellet boiler

Net Zero Energy Building technologies – Reversible Heat Pump/Organic Rankine Cycle coupled with Solar Collectors and combined Heat Pump/Photovoltaics – Case study of a Chilean mid-rise residential building

Heat demand calculation procedures for buildings are currently being conducted based on the Polish Standard grounded on the European Standard for heat losses methodology. Poland was divided into several climatic zones with given calculations and annual average external air temperature values. In each zone, the technical committee gives the temperature that must be considered. The data included in the Polish Standard preparation concern several years backwards. However, throughout the previous years, we have observed the tendency of the temperature to increase throughout the year, not only in Poland. The phenomenon provides scientists with the conclusion that the temperatures will continue to increase yearly. The low temperatures in the winter season will no longer occur. Therefore, it is necessary to analyse the possibility of lowering the heat demand calculation, including the actual prevailing temperature values. The study was conducted regarding possible economic benefits for the building users due to the lower temperature difference between the internal and external temperatures. Three types of heating systems were analysed. The calculations were conducted for air to water heat pump, pellet boiler and gas condensing boiler, proving that regarding the actual meteorological data, the average annual cost reduction will be in the range of 858 PLN to 1,035 PLN.

Abstract. Residential biomass combustion significantly contributes to light-absorbing carbonaceous aerosols in the atmosphere, impacting the earth's radiative balance at regional and global levels. This study investigates the contribution of brown carbon (BrC) to the total particulate light absorption in the wavelength range of 370–950 nm (BrC370–950) and the particulate absorption Ångström exponents (AAE470/950) in 15 different European residential combustion appliances using a variety of wood-based fuels. BrC370–950 was estimated to be from 1 % to 21 % for wood log stoves and 10 % for a fully automatized residential pellet boiler. Correlations between the ratio of organic to elemental carbon (OC / EC) and BrC370–950 indicated that a one-unit increase in OC / EC corresponded to approximately a 14 % increase in BrC370–950. Additionally, BrC370–950 was clearly influenced by the fuel moisture content and the combustion efficiency, while the effect of the combustion appliance type was less prominent. AAE470/950 of wood log combustion aerosols ranged from 1.06 to 1.61. By examining the correlation between AAE470/950 and OC / EC, an AAE470/950 close to unity was found for pure black carbon (BC) particles originating from residential wood combustion. This supports the common assumption used to differentiate light absorption caused by BC and BrC. Moreover, diesel aerosols exhibited an AAE470/950 of 1.02, with BrC contributing only 0.66 % to the total absorption, aligning with the assumption employed in source apportionment. These findings provide important data to assess the BrC from residential wood combustion with different emission characteristics and confirm that BrC can be a major contributor to particulate UV and near-UV light absorption for northern European wood stove emissions with relatively high OC / EC ratios.

Particulate matter emission characteristics of spruce, sunflower and maize: A comparison between nominal and reduced output in a small-scale boiler

Energy, exergy, environment and techno-economic analysis of hybrid solar-biomass systems for space heating and hot water supply: Case study of a Hammam building

Alternative energy currently has all the technical means that allow it to be considered a classic addition to traditional methods of energy production. Modern energy technologies require a more effective and reliable solution to the problem of energy supply based on the integrated use of various types of renewable energy sources, energy accumulators of various types, heat pumps, combined means of thermal modernization of buildings and alternative fuel energy backups. In modern heat supply systems using alternative energy sources, usually at least 2 heat sources are used - a renewable heat source and a traditional source as reserve and peak. The operation of gas, solid fuel, pellet and electric boilers, solar collectors, various types of heat pumps in the heat supply systems of buildings and civilian buildings is analyzed. The high-quality operation of the heat supply system is affected by various schemes of connecting consumers to heat generators. The specifics of the effective operation of the combined heat supply system are the coordination of various hydraulic “generator-consumer” modes. In practice, three approaches are used to coordinate the modes of operation of alternative heat supply systems with consumers: regulation of the power of the heat source, programming of heat consumption modes, introduction of heat accumulators. It is important to find out the conditions for the effective use of heat accumulators for intermittent heating mode, which can ensure a decrease in the thermal power of a heat generator operating in superheat mode. The operation of the pilot plant of the integrated system of alternative heat supply (ISAHS) was studied, the technical and economic indicators obtained for the heating period for three different types of heat generators: gas boiler, pellet boiler, heat pump were analyzed. An experimental study of the combined heat supply system for various heat supply facilities made it possible to establish that for public buildings, a rational way to increase their efficiency is the use of intermittent heating modes, a two-stage storage system, and coordination of structural and mode parameters of the main contours of the system. Keywords: combined heat supply system, boiler, solar collector, heat pump, heat accumulator