Decentralized Energy Supply Systems Research Articles

Ground-Mounted Photovoltaic and Crop Cultivation: A Comparative Analysis

Human civilization depends on energy sources, mainly fossil fuels. An increase in the prices of fossil fuels and their exhaustibility limit economic growth. Carbon dioxide emission causes global environmental problems. Global crises (including COVID-19) have sharpened food and energy supply problems. The decentralized energy supply systems as well as the expedition of the application of renewable energy may solve these challenges. The economic shift to renewable power generation intensifies the competition between food crop production and green energy for land. This paper applied an open-source spatial-based model to quantify the solar power generation (the ground-mounted photovoltaic panels) for the southern regions of Poland (the Opole region) and Ukraine (the Mykolaiv region). The model used technical, economic, and legal constraints. This study compared economic indicators of the solar power generation and the crop production projects for rain-fed land. The net present value (NPV) and the profitability index (PI) were used for the economic evaluation. Additionally, the coefficients of variation were determined to assess investment risks. The use of r.green.solar model to find the spatial distribution of the reduction of carbon dioxide emission was the novelty of this study. The analysis revealed that the PV projects have higher NPV, but lower PI compared to the crop production. The PV projects have lower coefficients of variation. This fact testifies that these projects are less risky.

БЕЗКАРБОНОВІ СИСТЕМИ ЕНЕРГОЗАБЕЗПЕЧЕННЯ ЖИТЛОВОГО ФОНДУ В КОНТЕКСТІ ЕНЕРГЕТИЧНОЇ БЕЗПЕКИ

The article analyzes the main features of the EU energy policy in the building stock, which is aimed at achieving climate neutrality by the middle of the current century. The main directions and technologies related to the energy and climate safety of energy supply systems of the building stock are highlighted. At the same time, special attention is paid to the need to transition to energy- and environmentally-efficient decarbonized centralized and decentralized energy supply systems with the prospect of full electrification of heat supply systems. The importance of further intensive development of energy storage systems in daily and seasonal cycles is indicated as an important condition of the carbon-free energy market. The possibility of using ecologically improved technologies of heat generation on natural gas within certain time limits is also noted.

Assessing shading losses of photovoltaic power plants based on string data

As decentralized energy supply systems are becoming more and more important for the global energy supply, – apart from a heightened focus on energy rationalization and energy efficiency – increasing the role of variable renewable energy sources, such as solar and wind energy, in energy consumption is gaining more and more significance. Since energy projects tend to be meant for the long term and involve considerable financial investments, it is indispensable to be aware of the country-specific regulatory background when establishing photovoltaic (PV) systems. The last few years have witnessed a trend that new PV power plants are mostly built using traditional crystalline PV technologies, which are prone to irreversible PV module damage due to shading effects. During the operation of PV power plants, anomalies causing loss of income and even fire hazard in extreme cases may occur. Thus, the identification of the problematic parts of the system is of utmost importance. This paper presents the energy relationships of shading by the example of a Hungarian PV system. The goal of this study is to introduce a methodology that can be used internationally to categorize the operational characteristics of the strings of PV power plants on the basis of monitoring data, which allows the assessment of the annual energy loss. The innovative novelty of the model is that its use can provide practical help for the operators of PV systems around the world, since the solution is easy to adapt to real-time supervisory and management platforms and it makes the localization of problematic strings possible, thusly allowing a more focused inspection of PV power plants. The novel practical benefit of the model is that by its use it becomes possible to detect any energy loss resulting from the spacing distance of the strings of PV power plants or faulty operation (the negative shading effects of trees and other objects, faulty inverter operation) by using a simpler calculating mechanism. The early detection of problems is essential for the protection of the PV modules, the subsequent reconstruction of the strings or even solving issues under guarantee. In addition, by assessing the annual energy loss caused by shading, it becomes possible to detect any negative change in the economic indicators of the investment.

Gravity Compressed -Air- Hydraulic- Power-Tower Energy Storage Plants

In the era of the increasing implementation of renewable energy sources in the electrical energy supply the demand for energy storage continues to grow. This is because the renewable energy sources, mainly in the form of wind and solar energy, are sustainable, but at the same time are subject to natural fluctuations. The wind does not always blow, and the sun does not always shine. Therefore, a stable and reliable power supply is more challenging than ever. It now must regulate fluctuating electricity demand and fluctuating electricity supply. At the same time decentralized energy supply systems based mainly also on PV and wind energy (e.g. as hybrid systems) storage requirement will become a key component of these local electrical energy supply networks especiallyy to balance the energy demand and supply. Among the many storage techniques an important example is the Hydro-Power-Tower an innovative hydraulic energy storage system based on pumped storage technology. Depending on the actual storage method that can be based on gravity (lifting / falling of weight in a vertical underground or above ground Tower), on air compression / decompression or on a combination of both techniques, can be distinguished the following Storage systems, Gravity Hydro Power Tower Storage (GHPTS), Compressed Air Hydro Power Tower Storage (CAHPTS) and Gravity Compressed Air Hydro Power Tower Storage (GCAHPTS).The GHPTS is the classic form of the Hydro Power Tower Storage and is widely discussed in the literature with scientific results and technical applications especially in the last decade. Besides the many advantages of (GHPTS) an important disadvantage is the very high weight and high cost of the tower piston (usually metal) which is the key component for potential energy storage. The storage based on Compressed Air is also widely applied in different storage systems but less so than Power Tower. Regarding the application of compressed air, in the PTS system, some own results are to mention, proposing a replacement possibility of the heavy overload piston of (GHPTES) using a part of the tower as a compressed air reservoir. The present study considers the combination of both storage techniques Gravity and Compressed Air integrated in a so-called Gravity-Compressed-Air-Hydro- Power- Tower - Storage (GCAHPTS). The combined influence of compressed air pressure and high of weight tower piston on the stored energy will be analysed. The obtained results allow the optimal design of such a combined power tower storage system. When the compressed air or high weight piston is missing on obtain GHPTS or CAPTS respectively.

Energy Consumption Optimization in Agriculture and Development Perspectives

In this article, indicators of energy consumption in agriculture for Russian Federation are discussed, starting from the year 1990, and their forecast values for the period up to 2030 with the analysis of the decay in the period from 1991 to 2010 and gradual growth of energy resources consumption started in 2010 and continued to the present day has been analyzed. The outlines of the strategy of rural energy base development and optimization have been considered. Demand, development, and implementation conditions of decentralized energy supply systems have been substantiated, and their features, composition, and application field have been specified. It has been shown that the major energy resource of standalone energy systems is local and renewable energy sources and of agricultural production wastes. Methods and technologies for the conversion of renewable energy sources (RES), biomass, and waste of agricultural production into heat and power have been characterized.

Resilient and Immune by Design Microgrids Using Solid State Transformers

Solid State Transformers (SST) may become, in the near future, key technological enablers for decentralized energy supply systems. They have the potential to unleash new technologies and operation strategies of microgrids and prosumers to move faster towards a low carbon-based economy. This work proposes a paradigm change in the hierarchically and distributed operated power systems where SSTs are used to asynchronously connect the many small low voltage (LV) distribution networks, such as clusters of prosumers or LV microgrids, to the bulk power system. The need for asynchronously coupled microgrids requires a design that allows the LV system to operate independently from the bulk grid and to rely on its own control systems. The purpose of this new approach is to achieve immune and resilient by design configurations that allow maximizing the integration of Local Renewable Energy Resources (L-RES). The paper analyses from the stability point of view, through simplified numerical simulations, the way in which SST-interconnected microgrids can become immune to disturbances that occur in the bulk power system and how sudden changes in the microgrid can damp out at the Point of Common Coupling (PCC), thus achieving better reliability and predictability in both systems and enabling strong and healthy distributed energy storage systems (DESSs). Moreover, it is shown that in a fully inverter-based microgrid there is no need for mechanical or synthetic inertia to stabilize the microgrid during power unbalances. This happens because the electrostatic energy stored in the capacitors connected behind the SST inverter can be used for a brief time interval, until automation is activated to address the power unbalance for a longer term.

Small Landowner Production of Pellets from Green, Beetle-Killed, and Burned Lodgepole Pine

To meet the growing need for raw materials to produce pellets and wood-based biofuels, trees killed by natural disturbances have increasingly been considered as potential feedstock in bioenergy development scenarios in the Western U.S. and Canada. While much research has focused on utilization of beetle-killed and fire-salvaged timber from federal lands in this region, small private landowners make up a large portion of land holdings in the Rocky Mountain Region and may also provide an important potential supply of uniform feedstock pellets in decentralized energy supply systems in the future. In this paper, we evaluated the quality of pellets produced from green, beetle-killed, and burned lodgepole pine with and without bark using a chipper, hammer mill, and pellet mill intended for use by small landowners. Results show that green, beetle-killed, and fire-salvaged lodgepole pine produced by small landowners, including material with bark, are suitable as feedstock for pellet production. Further, pellet quality can be varied through the blending of source lodgepole pine products when needed to meet pellet quality standards.

TRusT: A Two-stage Robustness Trade-off approach for the design of decentralized energy supply systems

The design of decentralized energy supply systems is a complex task and thus best addressed by mathematical optimization. However, design problems typically rely on uncertain input data, such as future energy demands or prices. Still, conventional optimization models are usually deterministic and thus neglect uncertainties. For this reason, the deterministic optimal solution is in general suboptimal or even infeasible. Robust design methods are available to guarantee security of energy supply, however, they usually lead to significant additional costs. In this work, we show that energy supply systems with guaranteed secure energy supply are not expensive per se. For this purpose, we propose the Two-stage Robustness Trade-off (TRusT) approach. The TRusT approach considers the trade-off between expected costs in the nominal scenario and costs in the worst case while guaranteeing security of energy supply. Thereby, the TRusT approach identifies balanced robust energy supply systems which are cost-efficient in both the daily business and the worst case. The TRusT approach can be applied and solved efficiently. In a case study, we identify robust design options which ensure security of energy supply at low additional costs. Hence, the TRusT approach is a suitable tool to design cost-efficient and secure energy systems.

An adaptive discretization MINLP algorithm for optimal synthesis of decentralized energy supply systems

Abstract Decentralized energy supply systems (DESS) are highly integrated and complex systems designed to meet time-varying energy demands, e.g., heating, cooling, and electricity. The synthesis problem of DESS addresses combining various types of energy conversion units, choosing their sizing and operations to maximize an objective function, e.g., the net present value. In practice, investment costs and part-load performances are nonlinear. Thus, this optimization problem can be modeled as a nonconvex mixed-integer nonlinear programming (MINLP) problem. We present an adaptive discretization algorithm to solve such synthesis problems containing an iterative interaction between mixed-integer linear programs (MIPs) and nonlinear programs (NLPs). The proposed algorithm outperforms state-of-the-art MINLP solvers as well as linearization approaches with regard to solution quality and computation times on a test set obtained from real industrial data, which we made available online.

CO2 reduction strategies for the Northern Netherlands

The concern about global warming initiated ambitious CO2 reduction goals in cities and regions in the Netherlands. This article describes a study of such a local initiative for the Northern Netherlands. The research aimed to develop CO2 reduction scenarios for 2035 with national and international politics, and regional goals and opportunities being integrated. The scenarios were calculated using a bottom-up model. Four scenarios were developed with a defined goal of a 50% CO2 reduction on the starting year (2000). The four scenarios were developed along two axes: centralized versus decentralized energy supply systems, and international climate policy versus a European-oriented energy policy. Primary energy consumption varied between 273 and 443PJ. Although 50% CO2 reduction is possible in all scenarios, an enormous effort would be required to reach this goal. Depending on the scenario: an almost 50% reduction of the primary energy demand, the installation of 4 GW of offshore wind or the shift to a bio based economy is needed.

Study of The Amount of Produced Animal Manure and Biogas Potential in a 5, 20 and 40 km Zone around Debrecen

The guiding principle for our research is that decentralized energy supply systems should be located near local consumers. One big, local market for energy from biogas plants in Hajdú-Bihar county is Debrecen. In the course of the investigation of biomass suitable for biogas production in the area of Debrecen, this study determines the quantity of biogas producible from animal manure. Municipalities around Debrecen were examined in circles with 40, 20 and 5 km radius. Livestock data of these settlements stem from the Agricultural Census in year 2000, actualized by the county trend of livestock changes. Manure quantity and biogas potential in these places are estimated with coefficients from the literature and our calculations. In the largest circle, about 1.4 million tons of manure is produced, from which round 94 million m3 biogas can be produced. Biomass produced in the settlements and producible biogas shows a remarkable trend of concentration, which supports our recommendation on the system of energy supply.

04/00270 Cost effectiveness of decentralized energy supply systems taking solar and wind utilization plants into account: Sontag, R. and Lange, A. Renewable Energy, 2003, 28, (12), 1865–1880. (In Japanese)

04/00270 Cost effectiveness of decentralized energy supply systems taking solar and wind utilization plants into account: Sontag, R. and Lange, A. Renewable Energy, 2003, 28, (12), 1865–1880. (In Japanese)

Cost effectiveness of decentralized energy supply systems taking solar and wind utilization plants into account

In this article, results are presented of annual simulations of a decentralized (regional) plant for the power and heat supply of a residential complex. This complex consists of four houses with 40 flats all in all. The annual power consumption of the complex is 157 MWh and the heat requirement is 325 MWh. The concrete dynamics of the energy demands over the year is taken into consideration. The energy supply system is composed of a power-controlled combined heat and power (CHP) plant (55 kW), a photovoltaic plant (PV array or PV plant) array for power generation as well as a field of solar thermal collectors with a short-term accumulator for water heating and a long-term accumulator for supplying heat for domestic heating purposes. Simulation results demonstrate that synergetic effects result from the combination of a CHP plant with wind power and PV plants of varying sizes, which have an effect on the cost effectiveness of the plant as a whole with the different dynamics of energy sources (wind and solar energies) and of the consumption of power and heat being the decisive factors. The power deficits of wind power and PV plants are compensated through the application of a natural gas-operated CHP plant. In almost all variants, the demand for fossil energy carriers is distinctly less than in conventional energy supply plants.

Low exergy reactor for decentralized energy utilization

A new conceptual reactor named ‘low exergy nuclear reactor (LER)’ was proposed and its possibility was discussed qualitatively. The LER is defined by the reactor that generates low-exergy energy at a temperature near environmental temperature between about 100°C and 300 °C, which is lower than the output temperature of the energy generated by the conventional light water reactors (LWR). The necessity of the LER was discussed based on the present energy technology trend. Cogeneration systems based on the LER combined with absorption heat pump, thermoelectric device and steam turbine were proposed for decentralized energy utilization. The enthalphy balance of those decentralized energy supply systems was evaluated using practical data. The thermal efficiency of the LER system was compared with that of conventional LWR system. The LER system was expected to be suitable for a decentralized heating and cooling system.

Decentralized energy supply: Suitability for the UK's industrial sectors

From the results reported here it is suggested that policy decisions about the potential contribution of decentralized energy supply systems to UK industrial energy requirements should be based on the suitability of individual sectors rather than averaged over all sectors. The suitability of decentralized energy sources is evaluated, based on a themodynamic match between source and demand. This suitability criterion is used to identify the most appropriate sector in manufacturing industries for the adoption of decentralized energy supply, leaving aside economic cost considerations and individual site requirements.