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Heat Flow
Published in Samuel C. Sugarman, HVAC Fundamentals, 2020
Heat transfer by convection is when some substance that is readily movable such as air, water, steam, or refrigerant moves heat from one location to another. Compare the words “convection” (the action of conveying) and “convey” (to take or carry from one place to another). An HVAC system uses air, water, steam and refrigerants in ducts and piping to convey heat energy to various parts of the system. As stated, when air is heated, it rises; this is heat transfer by “natural” convection. “Forced” convection is when a fan or pump is used to convey heat in fluids such as air and water. For example, many large buildings have a central heating plant where water is heated and pumped throughout the building to terminals, such as heating coils (aka heat exchangers). Fans move heated air into the conditioned space.
Prioritising Uses for Waste Biomass
Published in Subhas K. Sikdar, Frank Princiotta, Advances in Carbon Management Technologies, 2021
Roland Clift, Xiaotao Bi, Haoqi Wang, Huimin Yun
The results of Petrov et al. (2017) illustrate the point that, to avoid introducing significant health effects, DH plants without highly effective gas cleaning must be located away from population centres in order to avoid human exposure, for example to provide heating and, if CHP plants are used, some electrical power in small remote communities. For larger population centres, high efficiency gas cleaning (including NOx suppression) is essential, implying that plants must be large enough for this to be economically feasible (Guest et al., 2011). In centralised biomass-fired DH plants, Selective Catalytic Reduction can reduce NOx emissions by 80% whilst electrostatic precipitation can collect 90% of the particulate matter (Pa et al., 2011). Technologies to achieve significantly cleaner gas emissions are already available (Seville, 1997) and have been deployed in specific waste-to-energy and biomass fired plants (e.g., Tagliaferri et al., 2015; Tagliaferri et al., 2018). With efficient gas cleaning, conversion from heating plant at the scale of individual buildings to centralised heating plant can improve air quality; this has been one of the reasons for the continuing popularity of biomass-fired District Heating in the Nordic countries (EU, 2018; IEA, 2019). Concerns over local air pollution have prevented the development of at least one District Heating plant in BC (Lee, 2015) but there are signs of revived interest (BC, 2018b). To exploit this use of biomass to the maximum extent possible will probably require a high-profile demonstration plant with lower emissions than the existing demonstration plants in BC, as a route to greater public acceptance.
Thermodynamic sustainability assessment for residential building heating comparing different energy sources
Published in Science and Technology for the Built Environment, 2022
In almost all analyzed cases, except for the biomass, the main problem is the process of combustion of fossil fuels, whether in a thermal power plant (generation of electricity), or in a heating plant in case of district heating, or in a gas or coal boiler in a building (generation of low temperature heat). Direct production of low temperature heat through the combustionof fossil fuels is a highly irreversible process, with low exergy efficiency and small exergy sustainability index. In addition to this, it causes high CO2 emissions and a high environmental impact. Also, it is clearly visible that the usage of electricity for generation of heat is not justified. On the other hand, burning biomass is the opposite process from growing it. It is considered that the biomass, during its growth, uses CO2, which is further released to the atmosphere after combustion in a boiler. This quantity is considered equal, but the conversion factor for biomass CO2 emission 0.01307 kgCO2(kWh)−1 includes the fuel used for biomass transport and treatment. Hence, the calculated CO2 emission is the lowest in case of biomass, cca 0.0196 tCO2/a.
Economic contradictions of the waste-to-energy concept and emissions reduction plan (case study, Czech Republic)
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Vojtěch Stehel, Jaroslav Dvořák, Zdeňka Wittlingerová, Anna Petruželková
According to the results stated above, replacing lignite with MMSW in heating plants may cause an increase in NOX emissions from energy production (approximately 58%), although the waste incinerators meet the BAT requirements. The value of the indicator of particulate matter formation in the case of MMSW combustion (A) is similar to lignite (B), because the generation of direct emission of PM10 was negligible in the case of MMSW combustion (A). Compared to lignite combustion (B), NOX emissions from MMSW combustion (A) cause a larger value of the acidification indicator (approximately by 50%) and photochemical ozone formation (approximately by 60%). Indicator values similar to lignite combustion (B) can be achieved by combining natural gas with MMSW (D). Technical and economic options to reduce emissions of NOX in the case of MMSW combustion (A) should be the subject of further research. In addition, in the case of MMSW combustion (A), it was found that the value of the GWP indicator is comparable to natural gas combustion (C) because of a low share of biomass waste in municipal solid waste in the location of assessed MMSW combustion heating plant (Czech Republic).
Methane budget estimates in Finland from the CarbonTracker Europe-CH4 data assimilation system
Published in Tellus B: Chemical and Physical Meteorology, 2019
Aki Tsuruta, Tuula Aalto, Leif Backman, Maarten C. Krol, Wouter Peters, Sebastian Lienert, Fortunat Joos, Paul A. Miller, Wenxin Zhang, Tuomas Laurila, Juha Hatakka, Ari Leskinen, Kari E. J. Lehtinen, Olli Peltola, Timo Vesala, Janne Levula, Ed Dlugokencky, Martin Heimann, Elena Kozlova, Mika Aurela, Annalea Lohila, Mari Kauhaniemi, Angel J. Gomez-Pelaez
At the Puijo site, CH4 is measured with a CRDS instrument (Picarro G2301) on the top of a telecommunication tower (Leskinen et al., 2009), which is located 2o3 km from the centre of Kuopio town (111,200 inhabitants, 2015). The tower (sampling point 84 m above ground) is built on a hill that is about 150 m above the surrounding lakes. Possible anthropogenic CH4 sources include a waste landfill 10 km to the southwest, a wastewater treatment plant 5 km south-southeast, a district heating plant using a combination of peat, wood chips and heavy fuel oil as fuel 3 km south-southeast, and the tower itself (sewage ventilation) when the wind speed is low ( m/s). In the sector from southwest to north, there are no significant anthropogenic CH4 sources nearby.