Heat Plant Research Articles

A comparative co-simulation analysis to improve the sustainability of cogeneration-based district multi-energy systems using photovoltaics, power-to-heat, and heat storage

For an extensive decarbonization of district multi-energy systems, efforts are needed that go beyond today’s cogeneration of heat and power in district multi-energy systems. The multitude of existing technical possibilities are confronted with a large variety of existing multi-energy system configurations. The variety impedes the development of universal decarbonization pathways. In order to tackle the decarbonization challenge in existing and distinct districts, this paper calculates a wide range of urban district configurations in an extensive co-simulation based on domain specific submodels. A district multi-energy system comprising a district heating network, a power grid, and cogeneration is simulated for two locations in Germany with locally captured weather data, and for a whole year with variable parameters to configure a power-to-heat operation, building insolation/refurbishment, rooftop photovoltaic orientation, future energy demand scenarios, and district sizes with a temporal resolution of 60 s, in total 3840 variants. The interdependencies and synergies between the electrical low-voltage distribution grid and the district heating network are analysed in terms of efficiency and compliance with network restrictions. Thus, important sector-specific simulations of the heat and the electricity sector are combined in a holistic district multi-energy system co-simulation. The clearly most important impact on emission reduction and fuel consumption is a low heat demand, which can be achieved through thermal refurbishment of buildings. Up to 46% reduction in CO2 emissions are possible using the surplus electricity from photovoltaics for power-to-heat in combination with central heat storage in the district’s combined heat and power plant. Domestic hot water heated by district heating network in combination with power-to-heat conversion distributed in the district reduces the load on the distribution power grid. Even though the investigated measures already improve the sustainability significantly, providing the energy needed for the production of synthetic fuels remains the crucial challenge on the further path towards net-zero.

Integration of compressed air energy storage into combined heat and power plants: A solution to flexibility and economy

To achieve carbon neutrality, conventional coal-fired combined heat and power (CHP) plants require higher operation flexibility to improve the grid's accommodation for renewable energy. Based on the promising converging interests between compressed air energy storage (CAES) and CHP, a novel CHP-CAES system with higher operation flexibility, energy efficiency, and round-trip efficiency (RTE) is proposed in this paper. The novelty of this system is that the released compression heat of CAES during the charge process can be recovered by the CHP, and the heat consumed during the discharge of CAES comes from the primary district heating network (DHN) instead of CHP. Firstly, the theoretical feasibility of the proposed CHP-CAES system is verified. Then, the operation flexibility, energy efficiency, and RTE of the CHP-CAES system are investigated. Results show that when the output heat of the CHP-CAES system is the design value of 150 MW, the power overload capacity can be increased by 3.04 %, and the feasible minimum load is decreased by 2.00 % of the design power. The maximum energy efficiency of the CHP-CAES system is increased from 68.38 % to 69.57 %, compared with the separate CHP system. Besides, the RTE of the CAES component is increased from 64.35 % to 77.05 %. Further, optimized scheduling strategies of this CHP-CAES system are proposed for the renewables accommodation scenario. Results show that the imbalance between power provision and demand can be notably reduced from 416.68 MWh to 1.01 MWh after the integration of the CAES system. Moreover, the profitability of the CHP-CAES system also would be improved by 14,449CHY by adopting the proposed scheduling strategies on the reference day, benefiting from the time-of-use (TOU) electricity price.

A zoned group control of indoor temperature based on MPC for a space heating building

The traditional regulation of district heating (DH) system are mainly based on the central control in heat plants and/or in the substations. But the end-user control is becoming increasingly important in saving DH energy consumption. In view of this, a novel zoned group control method of indoor room temperature based on model predictive control (MPC) for a space heating building is proposed. Firstly, a room temperature simulation model based on IDA Indoor Climate and Energy (IDA-ICE) is developed for the experimental room, where the simulation result is validated by the measurements. But it is still difficult to use this model in the predictive control. Therefore, a resistor capacitor (RC) room temperature simulation model with parameters identified by IDA-ICE is proposed. A room temperature controller based on RC-MPC is developed and tested in the experimental room for model validation. Secondly, a DH building in Dalian, China is chosen for the case study. The IDA-ICE simulation results show that the temperature distribution in different rooms of the building is clearly uneven without end-user control. Corresponding targeted control strategies according to the temperature distribution should be used in different zones (cluster of rooms) to improve indoor thermal environment. Therefore, a zoned group control model based on RC-MPC for DH building room temperature is developed in MATLAB/Simulink, which adopts IDA-ICE for parameter identification in RC simulation model and utilizes RC model to predict the room temperature trajectory in the MPC controller. Results show that the proposed model can achieve active and dynamic room temperature control for different zones more precisely according to the changing heat load distribution. It is not necessary to define every room a group, instead, many rooms with similar conditions can be grouped in the same cluster, and temperature differences between rooms can be controlled within a reasonable range.

Analytical Methods for the Rapid Determination of Solid Biofuel Quality

AbstractFuel properties of solid biofuels are essential aspects for the energy‐efficient and low‐emission operation of biomass heat and power plants. Hence, fuel quality parameters are often defined and used for pricing in supply contracts. To simplify and accelerate analytical approaches, rapid analysis devices are required to determine fuel properties such as water‐ and ash content, calorific value, and chemical composition on‐site. This article gives an overview about available technologies and, if applicable, their current state of use as rapid analysis devices for solid biofuels.

Robust optimization of seasonal, day-ahead and real time operation of aggregated energy systems

This work proposes an approach for the robust operational optimization of Aggregated Energy Systems (AES) on three key time scales: seasonal, day-ahead and real-time hourly operation. The evaluation of all the three time-scales is fundamental for AESs featuring seasonal storage systems and/or units (such as combined heat and power plants) with yearly-basis constraints on relevant performance indexes or emissions. The approach consists in a rolling horizon algorithm based on an Affine Adjustable Robust Optimization model for optimizing both day ahead schedule (commitment and economic dispatch) and the decision rules to adjust the real-time operation. The robust optimization model takes as input (i) the day-ahead forecasts of renewable production and energy demands with their corresponding uncertainty, (ii) past and future expected performance of the units with yearly constraints, and (iii) target end-of-the-day charge levels for the seasonal storage system. These long-term targets are estimated by optimizing the operation over representative years defined on the basis of the past measured data. The proposed methodology is tested on three real-world case studies, featuring up to four short-term uncertain parameters (energy demands and non-dispatchable generation), yearly constraints and seasonal storage. Results shows that the proposed methodology meets the yearly constraints and safely manages the seasonal storage without shortages, while always meeting the energy demands (no shedding). In addition, the cost of short- and long-term uncertainty were evaluated by comparing the results of the robust rolling horizon with other two deterministic approaches, proving a limited increase.

Considerations for noise control design in retrofit Combined Heat and Power Plants for Healthcare Facilities

Combined Heat and Power (CHP) plants have gained popularity in industrial and institutional applications due to their ability to recapture and repurpose wasted heat energy from the power generation process, resulting in significant energy savings and carbon emission reductions. However, noise control considerations have become increasingly critical in retrofit CHP systems, particularly in healthcare facilities. Often, strict noise performance requirements must be met due to the proximity of residential communities and to ensure a comfortable healing environment for patients.This technical paper explores critical noise control considerations for retrofit CHP systems in healthcare facilities, focusing on a case study from Hamilton Health Sciences, a healthcare network in Ontario, Canada. The paper examines the design challenges of upgrading the existing CHP plants across three separate hospitals when addressing stringent sound performance, system ventilation, air tempering, and structural capacity limitations within a limited space. The paper also discusses the unique sound attenuation design solutions implemented to address these challenges.The case study demonstrates the successful implementation of combining noise control design, ventilation design, and structural design into one integrated solution, specifically to overcome common design challenges in retrofit CHP systems.

Sustainable waste-to-energy plant site selection by a hybrid method of geographic information system and evidential reasoning: A case study Guilan province

A new hybrid method of utilizing Evidential Reasoning (ER) approach and Geographic Information System (GIS) was applied to find the optimum location of a Combined Heat and Power (CHP) incineration plant in Guilan province. According to guidelines and prevailing conditions, thirteen criteria were analyzed and divided to three main sections of environmental, social and economic categories. Most of the data in the study were obtained from local organizations and satellite images. To weight the criteria, evidential reasoning was applied to aggregate the decision-makers’ opinions, and to find the potential sites; spatial analysis was done through the GIS. The result of suitability analysis indicates that about 0.07 % of total area of Guilan province is "the most suitable" region for the incineration plant and 0.05 %, 0.07 %, 2.77%, and 97.04 % are in the class of "suitable", "relatively suitable", "least suitable" and "limited". The areas with an area of larger than 40,000 m2 which is the necessary area for a 9 MW incineration plant were classified as alternatives for incineration CHP plant locations (A1-A7). All the locations were investigated to be near rural areas, which might bring inevitable harm to the adjacent communities. Also, the low amount of “most suitable region” and “suitable region” foster a sense of concerns, which should be addressed by applying a sustainable approach for preserving the environment. The techno-economic analysis presented in this study indicates that the project is not economically beneficial at all.

Simulation Analysis of High Radiant Heat Plant Cooling and Endothermic Screen Waste Heat Recovery Performance Based on FLUENT

In this article, we propose the endothermic screen model. The aim is to reduce the problems of the high temperature and low utilization of waste heat in industrial plants with high radiant heat. In this paper, the Rhino software is used to establish the model and import it into the FLUENT software, divide the mesh, set the boundary conditions and analyze the transient temperature field. Finally, the temperature change law in the plant and the waste heat recovery efficiency of the endothermic screen are obtained. The flow of cooling water in the endothermic screen is used to transform and transfer the high-radiation heat inside the plant to the outside. The simulation results show that after adding the endothermic screen, the average indoor temperature drops from 313.33 K to 305.66 K, which has a cooling effect. The waste heat recovery efficiency reaches up to 56%, and the waste heat recovery effect is obvious. The research results can provide a reference for the application of an endothermic screen in actual high radiant heat plants and provide a more comfortable working environment for the plant workers.

The Faster the Better? Optimal Warm-Up Strategies for a Micro Combined Heat and Power Plant

The warm-up process is a critical operation phase for micro Combined Heat and Power (mCHP) plants, directly impacting their efficiency, reliability, and lifetime. As small decentralized power generation units are increasingly expected to be operated on demand, start-ups will occur more frequently and thus the importance of the warm-up process will further increase. In this study, we address this problem by presenting a mathematical optimization framework that finds optimal actuator trajectories that significantly reduce the warm-up time and improve the thermal efficiency of an mCHP plant. The proposed optimization framework is highly flexible and adaptable to various objective functions, such as maximizing efficiency or minimizing the deviation from desired temperature references. The underlying mathematical model has been experimentally validated on a physical mCHP test rig. Selected case studies further demonstrate the effectiveness and flexibility of the framework and show that with the optimized actuator trajectories, the mCHP plant can reach its steady-state operating temperature in 40% less time. The results also indicate that the shortest warm-up time does not necessarily lead to the highest thermal efficiency. Accordingly, the methodology proposed in this paper provides a powerful tool to study higher-level operational strategies of mCHP plants and thus to maximize their overall performance, which directly translates into an improved operational cost-effectiveness, particularly in demand-driven energy landscapes.

Improving the UES of Russia Thermal Efficiency and Environmental Friendliness by Using Highly Maneuverable Gas Turbine Combined Heat and Power Plants

New trends in the fight against climate change on the globe, involving the reduction of greenhouse gas emissions, influence the formation of a new electric power system structure. Rapid development of renewable energy sources (RES) affects the electrical operation modes of power plants. As a result of the growing share of RES in the power systems of the European Union member states, a decrease in the electricity production in the cogeneration mode is observed in them. The structure of generating capacities must correspond to the heat and electricity consumption structure. To cover the daily load schedule non-uniformity, it is necessary to operate the generating equipment in semi-peaking and peaking modes. The introduction of highly maneuverable GTU-based CHPPs capable of operating in the cogeneration mode with daily startups/shutdowns can achieve significantly better efficiency of electricity production in the daily load schedule peak part. The introduction of 10 GW of highly maneuverable GTU-based CHPPs in the UES of Russia will make it possible to reduce the annual fossil fuel consumption by 19.6 million tce, CO2 emissions by 55 million t, and NOx emissions by 24.7 thousand t.

Potential to balance load variability, induced by renewable power, using rock cavern thermal energy storage, heat pumps, and combined heat and power in Sweden

Large shares of variable renewable electricity (VRE) generation increase the demand for flexible power balancing capacities for handling power surpluses and deficits. Within district heating (DH) production systems, electricity can be produced in combined heat and power (CHP) plants but also consumed in heat pumps, and thus contribute with balancing capacity. However, this power balancing potential in DH production units is limited by heat load variations. To improve the potential, large-scale thermal energy storage (TES) can be used to increase heat-load flexibility. This study investigates the power balancing capacity of 85 existing Swedish DH systems, with hypothetical access to rock cavern oil depots assumed to have been converted into TES units. In the study, the Swedish power load is assumed to be covered by 60 % wind and 10 % solar power. The results show that Swedish DH systems, on a national scale, could reduce power deficits and surpluses by approximately 9 % respectively. There will be competition between heat pumps and CHP units for DH load supply while providing power balancing services. The use of heat pumps could also, on national level, yield a reduced fuel use in DH production by about 10 % when compared to conventional DH system operation. The study highlights the impact the temporal distribution and annual shares of VRE surpluses and deficits have on the fuel use.

The Influence of Addition of Fly Ash from Astana Heat and Power Plants on the Properties of the Polystyrene Concrete

Due to the constant increase in prices for energy resources, as well as the reduction in non-renewable resources in most developed countries of the world, the energy consumption standards of buildings are constantly decreasing, and the requirements for the level of thermal insulation of building envelopes are increasing. The increasing requirements in the level of thermal insulation of enclosing structures make the issues of improving and developing new materials and products become more urgent. Polystyrene concrete has good high-thermal and sound-absorbing properties. This serves as a means of reducing costs, improving thermal insulation, reducing the dead load (weight) on the building and outside, among many other advantages. However, concrete made with polystyrene foam as a substitute for large aggregates has insufficient strength, due to the fact that the cement has low adhesion to the polystyrene foam. Based on the research of scientists and authors on the possibility of using industrial waste, it was assumed that the addition of fly ash to the composition would strengthen the matrix and the degree of compression of the polymers by the cement matrix as a result of the presence of nanoparticles in the fly ash and their positive effect on the structure and properties of the composition. The aim of the study was to develop a heat-insulating polystyrene concrete based on a binder using fly ash and to investigate its physical and technical properties. The properties of fly ash have been studied for the purpose of safe use in mixtures to increase strength properties and improve adhesion to polymers. The involvement of industrial waste from the ashes of coal from Kazakhstani deposits will contribute to the ecological improvement of the environment of the megacities of Kazakhstan. The effect obtained from the optimal combination of the characteristics for a building material is the improved physical and mechanical properties of heat-insulating materials.

Techno-Economic Assessment of an Off-Grid Biomass Gasification CHP Plant for an Olive Oil Mill in the Region of Marrakech-Safi, Morocco

A substantial number of off-grid olive oil mills in Morocco are powered by diesel-fired generators, which hugely contribute to air pollution and greenhouse gas emissions. In this research work, a biomass gasification combined heat and power (CHP) plant fueled with local by-products was explored as a renewable alternative to electrify off-grid olive oil mills in this country. The case study considered a gasification CHP plant with a rated power of 80 kWe, in order to enable adaptation of the producer gas flow rate to abrupt changes in the power generation unit under dynamic operation. A downdraft gasifier and a producer gas conditioning unit were modeled under steady state operation using Cycle-Tempo, while the power generation unit was modeled in the Thermoflex simulation environment under partial and full load operation. Olive cake pellets and olive pruning chips were evaluated as biomass feedstock, with moisture contents ranging from 5% to 20% (wet basis). The results from the simulation of the gasification CHP plant showed net electrical efficiencies and CHP efficiencies around 18% and 35%, respectively. Finally, a profitability assessment of the gasification CHP plant was developed for 2 months of continuous operation, together with a sensitivity analysis. The results for the baseline scenario reveal a payback period of 7–8 years and a 68.5% accumulated profit based on the capital investment, which suggest that biomass gasification CHP plants can represent an economically feasible and sustainable solution for the electrification of off-grid areas in Morocco.

Perspectives of Small-Scale Hydropower Engineering in Ukraine

Every country takes care of energy independence and security by using different energy sources and remarkably increasing electricity production by renewable energy sources. Ukraine is not an exception, especially when the energy infrastructure is significantly damaged during the war and there is a lack of capacities in the energy system. Because of this, the Government of Ukraine is planning a number of measures to launch systems of domestic mini-power plants.Ukraine has favourable conditions for developing the network of small-scale hydropower plants. While the hydropower potential of the largest Ukrainian rivers is used, the potential of small rivers is used only partially. The small-scale hydropower plants were built during the last century very actively. In 1912 the first small-scale hydropower plant was built. From 1923 to 1960, there were 956 hydropower plants with different capacities from a few kW to a few MW. However, at the end of the 1980s, the interest in small hydro decreased because of the construction of the large hydropower plants in the river Dniester and Dnipro, heat and nuclear power plants. Only 49 plants were in operation. Since 1995 the interest in small hydro has increased again. Nowadays, there are about 150 hydropower plants in operation.The paper examines the past and present state of small hydropower plants and perspectives on their development in the future, both by building new or reconstructing existing power plants. The list of hydropower plants with a short description of possible reconstruction is given. Moreover, the way of reducing the negative influence of hydropower plants on the environment is studied. Taking into account the energy issues in Ukraine, the possibilities of off-grid operation of hydropower plants are considered.The importance of energy security was evident from the issues that Ukraine is recently facing. Building new and reconstructing old small-scale hydropower plants will help to ensure the energy security of other types of electricity generation.

Hybrid (Gas and Geothermal) Greenhouse Simulations Aimed at Optimizing Investment and Operative Costs: A Case Study in NW Italy

Generally, greenhouses are high energy-consuming, sometimes accounting for 50% of the cost of greenhouse production. Geothermal energy plays a very important role in maintaining the desired temperature and reducing energy consumption. This work deals with a project of a hybrid heating plant (97% geothermal energy and 3% gas-condensing boiler) for the innovative Plant Phenotyping Greenhouse at the University Campus in Grugliasco (few km West of the city of Turin). The aim of the study is to testify to the energy efficiency of this kind of hybrid plant as well as its economic sustainability. Numerical simulations of a GRT were used to calibrate the system and verify that the software reasonably modeled the real case. They helped to correctly size the geothermal plant, also providing data about the thermal energy storage and production during on and off plant cycles. The results show a thermal power of 50.92 kW over 120 days of plant operation, in line with the expected energy needs to meet the base load demand. Long-term results further ensure a negligeable impact on the ground, with a thermal plume between 5 and 10 m from the plant, reducing substantially in a few months after switching off the plant.

Improved energy recovery from the condensed steam as part of HEN retrofit

The conventional approach to heat exchanger network (HEN) retrofit involving design techniques based on Pinch Technology (PT) is extended to include minimization of energy losses resulting from steam-condensate expansion. The authors proposed a new approach to minimize energy losses in utility system, thermally coupled with the combined heat and power (CHP) plant, using condensate subcooling phenomena. Moreover, applying condensate subcooling can counteract the drawbacks of commonly used multi-stage condensate expansion which increase operability and reduces investment and maintenance costs. A case study illustrates the suitability of improved condensate management as a HEN retrofit measure. The study object is a Methyl-Tert-Butyl Ether (MTBE) plant processing 18 t/h isobutylene and consuming 4386 kW of hot utility (steam) in the HEN. A study of the maximum possible heat recovery using PT indicates that the combined heat recovery from hot process streams and condensate can be increased by 510 kW compared to the existing state. At the same time, it is possible to generate additional power of 120 kW in the CHP plant that supplies energy to the MTBE plant. The locations of heat exchangers are accounted for in HEN reconfiguring. A new scheme of steam and condensate system is presented.

Four approaches for the year-round operation of wood-fired heating plants with low pollutant emissions

Fluctuations in heat demand and low heat demand in summer make it difficult to operate wood boilers all year round at high efficiency and low pollutant emissions. Therefore, today's wood-fired heating plants are often equipped with an auxiliary fossil fuel boiler. This paper investigates technical approaches to operate wood heating plants without additional fossil heat while avoiding unfavorable operation with high pollutant emissions. To evaluate these concepts, the dynamic behavior of wood-fired heating plants is modelled. The model includes one to four wood boilers, an auxiliary fossil fuel boiler, the heat demand, a stratified heat storage tank and the control system. The simulation reveals that the fossil share can be eliminated by large boiler output ranges and the use of several wood boilers in cascade. High storage capacities and large boiler output ranges enable low pollutant emissions and low cool down losses of the wood boilers. By doubling the storage capacity from 30 to 60 min of the nominal boiler output, reductions of the annual emissions of carbon monoxide and particulate matter of 17% and 8% are observed. Mitigating heat demand peaks can reduce pollutant emissions of heating plants with small storage capacity.

Influence of the transient operation of a large-scale thermal energy storage system on the flexibility provided by CHP plants

Among many technical options to improve the flexibility in combined heat and power (CHP) plants, thermal energy storage (TES) has attracted the most attention with its high applicability and benefit. Previous studies normally adopted a simplified approach for modelling a TES system, which assumes the optimized charged or discharged rate of heat can always be realized within the rated capacity. However, this may yield unfeasible results as the charging and discharging rates are dependent on the dynamic status of a TES, such as the state of charge (SOC) and water temperature, and the water flowrate for charging and discharging. In order to consider the transient operation of a TES, a 1D dynamic model was developed and validated against measured data from a real CHP plant. To analyze the dynamic performance of a TES, two key performance indicators (KPI), the maximum charging/discharging rate (C/D-ratemax) and the constant maximum charging/discharging rate that can be maintained constantly for one hour (CC/CD-ratemax) were employed. By doing simulations, it has been found that the CC/CD-ratemax was lower than the C/D-ratemax for most given SOCs of the studied TES. The developed model was also used to examine the optimized operation of a TES for providing flexibility. Some unfeasible results have been identified, as the optimized hourly charging/discharging rates were constrained by the CC/CD-ratemax. Therefore, it is of great importance to integrate a detailed dynamic model when optimizing the dispatch of electricity and heat for a CHP plant.

Environmental Assessment of Hellisheidi Geothermal Power Plant based on Exergy Allocation Factors for Heat and Electricity Production

The Hellisheidi geothermal power plant, located in Iceland, is a combined heat and power double-flash geothermal plant with an installed capacity of 303.3 MW of electricity and 133 MW of hot water. This study aimed to elucidate the environmental impacts of the electricity and heat production from this double-flash geothermal power plant. In this vein, firstly, the most updated inventory of the plant was generated, and secondly, a life-cycle assessment approach based on the exergy allocation factor was carried out instead of applying the traditionally used allocations in terms of mass and energy. The functional unit was defined as the production of 1 kWh of electricity and 1 kWh of hot water for district heating. The life-cycle stages included the (i) construction, (ii) operation (including abatement operations and maintenance), and (iii) well closure of the geothermal plant. All of the life-cycle stages from construction to dismantling were considered. Finally, the results on the partitioning of the environmental impact to electricity and heat with exergy allocations showed that most of the impact should be charged to electricity, as expected. Furthermore, the distribution of the environmental impacts among the life-cycle stages determined that the construction stage was the most impactful for the electricity and heat production. This result was attributable to the large consumption of steel that was demanded during the construction of the geothermal power plant (geothermal wells, equipment, and buildings). Impacts due to the abatement stage demonstrated that this stage satisfactorily reduced the total impact attributed to the three life-cycle stages of the geothermal power plant.

Determination of reliability conditions of reversible water supply systems in thermal power engineering

Today, the most important issues in the national economy of Ukraine are the issues of continuous, reliable and safe operation of reversible water supply systems, namely power units of thermal electric stations and heating plants of industrial enterprises. Trouble-free and reliable operation of water supply systems ensures the normal operation of social and household and industrial enterprises, as well as the safe operation of fire protection systems, which can be disrupted when the supply of a quality product to the consumer is stopped. For the purpose of research to determine the conditions of the reliability of reversible water supply systems in thermal power engineering, as well as the impact of risks in these systems on the reliability of reversible water supply systems, it is proposed to determine the states in which any water treatment system can be and the risks in water treatment systems that are technogenic in origin, and the consequences are ecological. The analysis of the obtained results showed that the states in which the water treatment system can be divided into three classes in accordance with the regulatory documents on the definition of technogenic risks in water treatment systems: class 1 (limit state) - the system works in normal mode, all blocks and elements work without failures and crashes; class 2 (critical state) - the system works in offline mode, some units or elements of the system work in partial failure mode; class 3 (dangerous state) - the system practically does not work and does not purify water, some blocks or elements of the system are in a state of failure. The risks that arise during the operation of water treatment systems and which can be used to assess their technogenic safety can be defined as: a) the probability of this system supplying raw water to the consumer as a result of the failure of blocks and elements of this system - state 3 - dangerous; b) the probability of this system supplying the consumer with poor-quality water as a result of partial failures and freelance work of units and elements of this system - state 2 - critical; c) the probability of this system supplying raw water to the consumer when the system is in state 1 - limiting, due to the natural inertia inherent in the specific physical and chemical processes on which the actual system operates.