Heat Plant Research Articles

Benefits of integrating power-to-heat assets in CHPs

Integrating power-to-heat (P2H) assets in combined heat and power plants (CHPs) is an attractive option, which can improve the flexibility in CHPs. This paper compares the potential benefits of integrating an electrical boiler (EB) and a heat pump (HP) in a CHP from providing flexibility services in both the day-ahead market and the frequency regulation market. An optimization model is developed for the operation of P2H assets and the CHP to maximize the profit. A case study is carried out using the data of a real CHP and electricity prices of Nord Pool. It is found that when an EB or a HP is integrated, the annual profit of the studied CHP from providing frequency regulation can be increased by 3.1 % (EB) or 27.7 % (HP) respectively compared to the CHP without P2H. Despite the high capital cost, a HP can increase the net present value up to 21.8 %, and achieve a payback period of 3 year, which are better than an EB (0.8 % and 5 year). Sensitivity analysis shows that prices of fuel and electricity have significant impacts on the net present value and payback period for the integration of P2H assets. Even though the increase of the fuel price decreases the NPV, it can lead to a decline in the payback period. Meanwhile, the increase of the electricity price results in a large growth in the profit and NPV, but a big reduction in payback period.

Modeling the development of a carbon capture and transportation infrastructure for Swedish industry

This work presents and applies a mixed integer programming (MIP) optimization model that minimizes the net present costs for CO2 capture and storage (CCS) systems for cases with defined emissions costs and/or capture targets. The model covers capture from existing large point sources of CO2 emissions in Sweden, liquefaction, intermediate storage and transportation using trucks to hubs on the coast, followed by ship transport to a storage location (excluding storage cost). The results show that the capture and transportation infrastructure, in terms of both the sites chosen for capture and the associated transportation setup, differs depending on whether the system is incentivized to capture biogenic or fossil CO2, or both. Waste-fired combined heat and power (CHP) plants are only chosen for capture at scale when biogenic capture targets and fossil emissions costs are combined, since the emissions from these sites comprise a combination of biogenic and fossil CO2. The value for the system in mitigating the costs from fossil CO2 emissions exceeds the increased cost of BECCS at waste-fired CHPs compared to larger pulp mills given the fossil emissions cost development assumed in this work. Although the cost for capture and liquefaction dominates the total cost of the CCS system, it is not the only factor determining the choice of sites for capture. Proximity to transport hubs with short offshore transportation distances to the final storage location is also an important factor. For the transportation infrastructure, it is shown that the cost for ships is the main cost driver.

Environmental and Architectural Solutions in the Problem of Waste Incineration Plants in Poland: A Comparative Analysis

Thermal waste transformation plants (waste incineration plants) are a strong architectural accent in the existing site context. They often function as power plants or combined heat and power plants, producing heat and/or electricity by recovering energy from flue gases. The main objective of this study was to demonstrate the relationship between the architectural quality and protection of the natural environment through the technological solutions applied. The indirect aims of the study include the demonstration of the educational message conveyed through architectural and environmental solutions. The relationships defined by the objective were verified in comparative studies of eight operating waste incineration plants in Poland, located in: Bialystok, Bydgoszcz, Konin, Krakow, Poznan, Rzeszow, Szczecin, and Warsaw. The results were presented in three problem areas: (i) architectural quality, (ii) environmental solutions, and (iii) educational message. The results of the study led to the following conclusions: (i) waste incineration plants operating in Poland show a relationship between the architectural quality and broadly understood pro-environmental solutions, (ii) and all waste incineration plants operating in Poland show educational solutions.

Optimized Operation and Sizing of Solar District Heating Networks with Small Daily Storage

To continue improving the integration of solar thermal in district heating networks, optimization tools that can study both sizing and operation of heating plants are needed. In this article, the ISORC tool was used to study the sizing and coupled operation of smaller storage and solar fields with other heating sources such as biomass and gas boilers. For this, a k-medoids algorithm was applied to select consecutive characteristic days to size the system based on an optimal operation of consecutive days in the same season. The formulated problem was nonlinear, and the objective function to be minimized was the total cost. Two case studies with different day constructions and distributions were studied with various sensitivity analysis. The formulation and methodology allowed us to study different cases and situations easily and proved the importance of the selection and attribution of typical days. In all cases, the results showed that even with a daily approach, solar thermal covers approximately 20% of the demand, which demonstrates the relevance of considering and developing small daily storage with small solar fields.

Optimal placement and sizing of photovoltaic power plants in power grid considering multi-objective optimization using evolutionary algorithms

During the past decade, the effect of renewable and non-renewable Distributed Generation (DG) sources of production has grown all over the world. Also, it has enhanced by national and international policies aimed at increasing the share of renewable energy sources and combining small high efficient heat and power plants to reduce greenhouse gas emissions, and global warming have been encouraged. Although the installation and operation of DGs have discussed for solving network problems in distribution networks, the fact is that in most cases, Distribution System Operator has no control or influence over DG placement and size. In this article, a meta-heuristic algorithm for management and decision-making for optimal selection is presented, and in choosing the optimal solution, the impact factor is suggested in the best case. Inappropriate DG placement may increase system losses, network investment, and operating costs. This paper determined the optimal capacity and placement of photovoltaic sources to reduce losses, improve the voltage profile, and increase the active power to reactive power lines in MATLAB software by the second version of the genetically engineered algorithm with unstable Non-dominated Sorting Genetic Algorithm (NSGA-II).

Distributionally robust day-ahead combined heat and power plants scheduling with Wasserstein Metric

Combined heat and power (CHP) plants are main generation units in district heating systems that produce both heat and electric power simultaneously. Moreover, CHP plants can participate in electricity markets, selling and buying the extra power when profitable. However, operational decisions have to be made with unknown electricity prices. The distribution of unknown electricity prices is also not known exactly and uncertain in practice. Therefore, the need of tools to schedule CHP units’ production under distributional uncertainty is necessary for CHP producers. On top of that, a heating network could serve as a heat storage and an additional source of flexibility for CHP plants. In this paper, a distributionally robust short-term operational model of CHP plants in the day-ahead electricity market is developed. The model accounts for the heating network and considers temperature dynamics in the pipes. The problem is formulated in a data-driven manner, where the production decisions explicitly depend on the historical data for the uncertain day-ahead electricity prices. A case study is performed, and the resulting profit of the CHP producer is analyzed. The proposed operational strategy shows high reliability in the out-of-sample performance and a profit gain of the CHP producer, who is aware of the temperature dynamics in the heating network.

Combined Heat and Power Economic Dispatching within Energy Network using Hybrid Metaheuristic Technique

Combined heat and power (CHP) plants have opportunities to work as distributed power generation for providing heat and power demand. Furthermore, CHP plants contribute effectively to overcoming the intermittence of renewable energy sources as well as load dynamics. CHP plants need optimal solution(s) for providing electrical and heat energy demand simultaneously within the smart network environment. CHP or cogeneration plant operations need appropriate techno-economic dispatching of combined heat and power with minimising produced energy cost. The interrelationship between heat and power development in a CHP unit, the valve point loading effect, and forbidden working regions of a thermal power plant make the CHP economic dispatch’s (CHPED) objective function discontinuous. It adds complexity in the CHPED optimisation process. The key objective of the CHPED is operating cost minimisation while meeting the desired power and heat demand. To optimise the dispatch operation, three different algorithms, like Jaya algorithm, Rao 3 algorithm, and hybrid CHPED algorithm (based on first two) are adopted containing different equality and inequality restrictions of generating units. The hybrid CHPED algorithm is developed by the authors, and it can handle all of the constraints. The success of the suggested algorithms is assessed on two test systems; 5-units and 24-unit power plants.

A comprehensive analysis of chemical and biological pollutants (natural and anthropogenic origin) of soil and dandelion (Taraxacum officinale) samples.

A range of analytical methods (GC-MS, LC-MS, voltammetry, microbiological and microscopic techniques, PCR) was used to assay a range of potential chemical and biological contaminants in soil and dandelion samples. The results provide the first comprehensive safety analysis of dandelion as a herbal product. Samples were collected from three different sites in Poland where the local population collects dandelion plants for their own consumption: Rudenka (a mountain meadow in the European Ecological Network of Natura 2000 protection area, free of agrotechnical treatments for over 30 years), Warszawa 1 (dense single-family housing with heavy traffic), and Warszawa 2 (recreation area with heavy traffic near a coal-fired heat and power plant). The assays of heavy metals and other chemical pollutants (PAHs, PCBs, dioxins, pesticides, mycotoxins) confirm that all collected soil and dandelion samples were chemically pure; however, 95 species of pathogenic bacteria were detected, including "carnivorous" Vibrio vulnificus, zoonotic Pasteurella pneumotropica, Pasteurella canis, Staphylococcus pseudintermedius, Staphylococcus lentus and Francisella tularensis as well as 14 species of pathogenic fungi and one protozoan parasite (Giardia intestinalis). The discovery of septicemia agents V. vulnificus, Fusobacterium mortiferum and Rahnella aquatilis in the soil surrounding dandelion roots and in the flowers, G. intestinalis in dandelion leaves and roots samples, all collected in Warsaw, is highly disturbing. This finding underlines the need for increased caution when collecting dandelion in densely populated areas with a large population of pets. Thorough washing of the harvested plants is necessary before using them for consumption, especially in the case of making salads from fresh dandelion leaves, which is becoming increasingly popular among people leading healthy and an environmentally friendly lifestyle.

MAINTENANCE MANAGEMENT SYSTEM OF HEP POWER PLANTS

Asset maintenance in power utilities is the key component of management. To this end HEP launched a project for the introduction of a maintenance management system (MMS) in its daughter companies engaging in the generation of electricity and in the generation and distribution of heat. The purpose of the MMS project was to set up a single management system the for technical systems of these facilities and to support it by implementing a specialised IT system. The paper describes the role of such systems in managing the operations of power utilities. It also shows the basic modules and functionalities in the MMS software for managing maintenance activities and logistic functions of managing inventories and procurement, the course of its introduction, and the performance in HEP’s power and heat plants.

Feasibility of implementation of solar thermal energy in steam-assisted gravity drainage (SAGD) in extra-heavy oil field in Colombia

The feasibility of implementing solar thermal energy in enhanced oil recovery (EOR) projects in Colombia has been practically avoided mainly owing to its high operating cost. However, Solar thermal energy can enable generating steam to be used for the EOR process with SAGD. Based on the amount of steam needed for an extra-heavy oil project, a solar thermal parabolic trough heat plant of 76.6 MWt for field application was designed to produce up to 261 MMBTU/h from computer simulated studies. This plant can generate injection steam during day hours and can be complemented with a steam conventional generation system for operating during night hours and on highly cloudy days. The obtained results showed the generated solar steam can contribute an average of 37.5% total daily steam requirement. By applying System Advisor Model (SAM), the produced solar steam can generate a saving of US$ 27602/day, which is signification saving of US$ 10.07 MM in one year. Therefore, the solar thermal parabolic trough heat technology can be a suitable option to implement in the Colombian Eastern Llanos Basin for thermal EOR.

Energy Evaluations of a New Plant Configuration for Solar-Assisted Heat Pumps in Cold Climates

Heat pumps in buildings allow for the limiting of CO2 emissions by exploiting directly the renewable energy available in the external environment (aerothermal, hydrothermal and geothermal sources). Moreover, other renewable technologies such as active solar systems can be integrated easily into use with them. This combination not only increases the share of primary energy provided by renewable sources for heating/cooling but also improves the heat pump performance indices. Nevertheless, in cold climates, air–water heat pumps should be equally penalized due to the unfavorable outdoor air temperature. Conversely, a water–water heat pump, connected with a solar tank and thermal solar collectors, overcomes this issue. Indeed, the higher temperature attainable in the cold source allows for reaching greater COPs, and when the solar tank temperature level is enough, emitters can be directly supplied, avoiding the absorption of electric energy. In this paper, this plant configuration, in which a further tank after the heat pump was considered to manage the produced thermal energy, is investigated. Proper control strategies have been developed to increase the renewable share. Regarding a reference residential building located in Milan, for which the water–water heat pump was sized properly, a parametric study, carried out in TRNSYS by varying solar tank volume and collecting surface, has allowed for the identification of the optimal system configuration. A renewable share, ranging between 54% and 61% as a function of the collecting surface and the storage volume, was detected, as was an average seasonal coefficient of performance (SCOP) over 4. Regarding two common heating plant configurations using an assisted PV air-to-water heat pump and a gas boiler, the optimal solution allows for the limiting of CO2 emissions by 33% and 53%, respectively.

Effects of heat treatment, plant coagulant, and starter culture on sensory characteristics and volatile compounds of goat cheese

The effects of heat treatment, coagulant source, and starter culture addition on the physicochemical, sensory characteristics, and volatile compounds of goat cheese were evaluated. For this purpose, the goat cheese was produced from raw milk or heat-treated milk coagulated with Cynara cardunculus L. protease or calf rennet. The effect of the starter culture addition was also investigated. No significant differences were observed between the cheeses produced using different coagulants in terms of chemical, microbiological and sensory parameters, and proteolysis levels, but the combination of heat treatment and starter culture addition affected most of the attributes. A total of 27 volatile compounds, including acids, alcohols, esters, ketones, and aldehydes, were identified in the cheeses during ripening. Acidic compounds were the most abundant volatiles in cheeses. The raw milk cheeses had the highest sensory scores, while an unpleasantly bitter taste was recorded for the heat-treated and starter-free milk cheeses.

Characterisation of the vertical temperature gradient in the canopy reveals increased trunk height to be a potential adaptation to climate change

Given the important role of temperature in vine development and grape composition, climate change has already impacted wine production. Adaptation strategies are needed in order to sustain the production of wines and maintain their typicity. Several levers of adaptation are possible, including the use of more heat and drought tolerant plant material, relocating the vineyard and adaptations in the cellar. The training system is also a potential lever for adaptation that is relatively easy to implement. Taking that avenue, a study of the vertical thermal gradient in the vine canopy was carried out in order to determine whether trunk height could be an adaptation strategy for manipulating micro-climate in the bunch zone. Temperature was measured at four different heights from the soil (30, 60, 90 and 120 cm) in two adjacent vineyard parcels. One parcel was managed with cover crop and the other by tilling the soil. The results of this study show that increased trunk height is not likely to significantly delay ripeness, but it could minimise the potential damages of both frost and heat wave events. Type of parcel management was found to have an effect: close to the ground, the cover crop parcel generally had lower minimum temperatures and higher maximum temperatures in comparison to the tilled parcel, exposing the vines to an increased risk of both frost and heat wave damage. When investigating the factors driving the vertical thermal gradient, soil moisture and weather type were found to have an impact. Some of these factors, like mean temperature and soil moisture, may exacerbate the vertical temperature gradient of maximum temperature in a climate change context and increase the risk of damages due to extreme temperatures.

Optimal management and data-based predictive control of district heating systems: The Novate Milanese experimental case-study

This paper addresses the modelling and optimal control of district heating systems connected to the electrical grid, with the goal of maximizing their operational efficiency and enabling the participation to electricity markets. Being these systems governed by nonlinear large-scale dynamical models, a novel procedure is proposed, which enables to obtain suitable models for optimization, and consisting in a combination of physical and identified piece-wise linear models. A two-phase optimization and control scheme is then designed, including an offline scheduling problem for participating to the day-ahead energy market, and an online Model Predictive Control system, minimizing the energy consumption of thermal generators while properly satisfying the users thermal demand. The proposed methodology is developed considering a real district heating plant, owned by the energy company A2A S.p.A. and supplying the city of Novate Milanese (Italy), and different experiments on the plant have been carried out. The experimental results and achieved performances are promising, showing a significant reduction of the operational costs and overall gas consumption.

Optimisation of an Integrated System: Combined Heat and Power Plant with CO2 Capture and Solar Thermal Energy

This paper aims to evaluate different design configurations of a combined heat and power (CHP) plant with post-combustion CO2 capture. Three cases are involved in this study: case 1 consists of three trains and each train has a configuration of one gas turbine with a heat recovery steam generator (HRSG); case 2 consists of three trains and one steam turbine; and case 3 consists of only two trains. The third case presented the highest CHP efficiency of 72.86% with 511.8 MW net power generation. After selecting the optimum configuration, a parabolic-trough collector (PTC) was incorporated to generate additional saturated steam at 3.5 bar for the capture plant, adding greater flexibility to the CHP because more steam was available. In addition, the efficiency of the cycle increased from 72.86% to 80.18%. Although case 2 presented lower efficiency than case 3, it has a steam turbine which brings the possibility of increasing the amount of electricity instead of steam production. When the PTC was incorporated in case 2, the power generated in the steam turbine increased from 23.22 MW to 52.6 MW, and the net efficiency of the cycle from 65.4% to 68.21%.

Process Economy of Alternative Fuel Production from Sewage Sludge and Waste Celluloses Biomass

The treatment and disposal of sewage sludge is one of the most important and critical problems of wastewater treatment plants. 8.7 million tonnes of dry matter of sewage sludge were produced annually in the European Union in the year 2020. Due to the fact that sewage sludge contains a large number of substances that are not beneficial for human health, the conditions for sludge management will be significantly tightened in the EU countries. One option for sludge liquidation is the production of biofuel in a form of granules or pellets from sewage sludge enriched by waste celluloses. The achieved results show that the resulting quality of such alternative biofuel is fully comparable to conventional fossil fuels. The economic analysis is based on the simulation of cash flows associated with the implementation of the project over the lifetime and the calculation of levelised cost (LCOE). Results shows (under the current economic situation) that solar dryer technology ensures the lowest LCOE at the level of 26 EUR/GJ in fuel. If the LCOE of the alternative biofuel includes the price of the saved emission allowance and the future costs of sewage sludge disposal, the resulting price is directly competitive with lignite. The results thus clearly show that there is an ecological and economically competitive substitute for solid fossil fuels, which may be an important step for the future use of local combustion sources such as district heating plants.

INFLUENCE OF PRESSURE IN THE TURBINE CONDENSER ON HEAT SUPPLY EFFICIENCY OF NPP WITH HEAT PUMP

The use of a heat pump for heat supply makes it possible to practically stop thermal pollution of the environment during the operation of thermal and nuclear power plants in winter. If a steam turbine condenser is used as a low-potential energy source for heat pump, the amount of released thermal energy will be equal to the sum of the thermal power of the NPP condenser and the power of the heat pump compressors. From the point of view of environmental safety, heat supply by combining power plant with a heat pump is an urgent task. But it is known that the due to the lack of steam extraction for water heating, the additional electrical power of the cogeneration heat and power plant will be less than the capacity of the heat pump compressors. Thus, in terms of thermodynamic efficiency, the use of a heat pump loses to a traditional cogeneration plant. The purpose of the work is to determine the influence of the final pressure in the turbine condenser on the thermodynamic efficiency of a nuclear power plant with a heat pump. A mathematical model of the thermal scheme of the K-1000-5.8/1500 NPP turbo-plant during summer and winter operation with heating plant has been developed. With the heating plant capacity of 230 MW, the electric capacity of NPP unit decreases by 43.5 MW. A mathematical model of a heat pump has been developed, for which a steam turbinecondenser is used as a low-potential energy source. To ensure the release of 230 MW of heat, the power of the heat pump compressor must be 48.4 MW. Thus, if the heating plant is replaced with a heat pump of the same capacity, the electric power will decrease by 4.8 MW. Calculations were made regarding the influence of the final pressure in the condenser on the exergetic efficiency of the NPP with heat pump, which uses the entire capacity of the turbine condenser. The analysis of the obtained results showed that the exergetic efficiency due to the increase in electric power released in winter increases with the increase of the final pressure in the condenser. This is explained by an increase in the heat pump coefficient of performance.

AERMOD air dispersion modeling and health risks of gas and oil fueled heating plant emissions

A significant part of the population in Serbia relies on central heating systems during the winter months, with around fifty heating plants in operation across the country. Common fuels used in these plants primarily include fossil fuels such as fuel oil and natural gas. Combustion of some of these fuels leads to significant emissions of air pollutants. This study evaluates the impact on the air quality of the two heating boilers at the Valjevo city (Serbia) heating plant. Air emissions were measured separately for two heating boilers in the facility using standard reference methodology. The AERMOD air dispersion model was used to estimate the dispersion of various pollutants. A combination of topographical and meteorological data was used to set up a receptor grid exposed to air pollution within a 10 km radius around the heating plant. It was found that the resulting distribution and concentration gradient of pollutant gases and particles were less inclined towards the city centre and instead spread eastwards into the surrounding villages. The health risk from the fuel oil boiler was shown to be significantly higher than that caused by the natural gas-fuelled boiler. Nevertheless, the calculated carcinogenic and non-carcinogenic health risks were within acceptable limits. However, further research is required to adequately assess the cumulative health risk generated by other surrounding emitters.

Computer thermodynamic modeling of the producing silicon alloys from the Kentau Combined Heat and Power Plant ash

The article presents the results of studies on the production of silicon alloys from the Kentau Combined Heat and Power Plant ash by the computer thermodynamic modeling method using the HSC-6.0-Chemistry software package. The effect of temperature (from 500 °C to 2000 °C) and the amount of carbon (from 30% to 40% of the ash mass) on the equilibrium distribution degree of elements between the condensed and gas phases, the grade of resulting ferroalloys. In the system under consideration, the formation of FeSi25 ferrosilicon occurs in the temperature range of 1500-1530 °C, and FeSi45 ferrosilicon-at the temperature of 1610-1700 °C; FS50 ferrosilicon is formed in the temperature range of 1700-1900 °C in the presence of 30% of carbon. The formation of FeSi45A10 ferrosilicoaluminium is possible at 2000 °C and 30% of carbon, in this case the concentrations of the metals in the alloy are 46.51% of Si, 8.57% of Al; 42.27% of Fe. FeSi45A15 ferrosilicoaluminium is formed in the system at 40% of carbon and 2000 °C; the elements’ concentrations in the alloy are 45.62% of Si, 14.76% of Al, 37.29% of Fe. Processing of 1 tonne of the ash makes it possible to produce 459 kg of FeSi45A10 ferrosilicon

Sales of electricity from cogeneration plants on organized markets in Southeast Europe

Volatile energy prices in the past period, force countries and their market participants to find alternative and cheaper sources of electricity production, while respecting defined environmental principles. Serbia is one of the rare European countries that uses its reserves of dissolved gas in the heat and electricity production. Combined heat and power plants, although in an almost negligible amount, contribute to the diversification of Serbia's production mix. With the presence of organized markets and local power exchanges, sale of electricity from combined heat and power plants is guaranteed for all producers who do not meet the conditions for acquiring the right to feed-in tariffs. The aim of this paper is to analyze the most profitable sale on the power exchanges of the domestic market and the region, specifically the markets of Serbia, Croatia, Hungary, Romania, and Bulgaria. The calculation methodology itself implies the use of average monthly price value for the observed markets, in the period of the past three years and nine months. In addition to the aforementioned, the costs of cross-border capacities were considered. In order to have a clearer overview of the results and the possibility of applying the methodology, the amount for calculation is 1 MWh. Costs and revenues related to negative and positive balance energy deviations are excluded from the analysis. Results showed that sale of electricity is most profitable on Serbian power exchange.