Heuristic optimization of clusters of heat pumps: A simulation and case study of residential frequency reserve

The technological challenges of adapting energy systems to the addition of more renewables are intricately interrelated with the ways in which markets incentivize their development and deployment. Households with own onsite distributed generation augmented by electrical and thermal storage capacities (prosumers), can adjust energy use based on the current needs of the electricity grid. Heat pumps, as an established technology for enhancing energy efficiency, are increasingly seen as having potential for shifting electricity use and contributing to Demand Response (DR). Using a model developed and validated with monitoring data of a household in a plus-energy neighborhood in southern Germany, the technical and financial viability of utilizing household heat pumps to provide power in the market for Frequency Restoration Reserve (FRR) are studied. The research aims to evaluate the flexible electrical load offered by a cluster of buildings whose heat pumps are activated depending on selected rule-based participation strategies. Given the prevailing prices for FRR in Germany, the modelled cluster was unable to reduce overall electricity costs and thus was unable to show that DR participation as a cluster with the heat pumps is financially viable. Five strategies that differed in the respective contractual requirements that would need to be agreed upon between the cluster manager and the aggregator were studied. The relatively high degree of flexibility necessary for the heat pumps to participate in FRR activations could be provided to varying extents in all strategies, but the minimum running time of the heat pumps turned out to be the primary limiting physical (and financial) factor. The frequency, price and duration of the activation calls from the FRR are also vital to compensate the increase of the heat pumps’ energy use. With respect to thermal comfort and self-sufficiency constraints, the buildings were only able to accept up to 34% of the activation calls while remaining within set comfort parameters. This, however, also depends on the characteristics of the buildings. Finally, a sensitivity analysis showed that if the FRR market changed and the energy prices were more advantageous, the proposed approaches could become financially viable. This work suggests the need for further study of the role of heat pumps in flexibility markets and research questions concerning the aggregation of local clusters of such flexible technologies.Comisión Europea 69596

Report on a Plus-Energy District with Low-Temperature DHC Network, Novel Agrothermal Heat Source, and Applied Demand Response

District heating and cooling networks can pose the possibility of including a variety of renewable energy sources as well as waste heat into a district’s heat supply concept. Unfortunately, low demand densities as they increasingly occur through higher building energy standards and in rural areas render conventional heating and cooling networks inefficient. At the same time, power-to-heat is becoming more and more important to make use of a larger amount of renewable energy sources on the electrical side by providing more flexibility by means of demand response and demand-side management. Within this work, a rural Plus-Energy settlement is presented addressing those topics by a low-temperature district heating and cooling network connected to a novel agrothermal collector supplying 23 residential buildings with decentralized heat pumps and PV systems. The collector, the network, and six of the buildings are equipped with comprehensive monitoring equipment. Within those buildings, forecast and optimization algorithms are implemented to adapt their heat pump operation to enable an increase of self-consumption, to include flexible electricity tariffs, and also to participate in power markets. Thereby, for the low-temperature district heating and cooling network, it has been shown that the concept can operate in the future at competitive heat costs. On the building level, up to 50% of cost savings could be achieved under ideal conditions with the optimization of the self-consumption of PV electricity. However, to ensure optimal results, the individual system components have to be dimensioned for this task

A set of comprehensive indicators to assess energy flexibility: a case study for residential buildings

The increasing share of renewable energy sources in the power industry poses challenges for grid management due to the stochastic nature of their production. Besides the traditional supplyside regulation, grid flexibility can also be provided by the demand side. Demand-Response is an attractive approach based on adapting user demand profiles to match grid supply constraints. Nevertheless, defining the flexibility potential related to buildings is not straightforward and continues to pose challenges. Commonly accepted and standardized indicators for quantifying flexibility are still missing. The present paper proposes a new quantification methodology to assess the energy flexibility of a residential building. A set of comprehensive indicators capturing three key elements of building energy flexibility for demand response, notably, capacity, change in power consumption and cost of the demand response action have been identified. The proposed methodology is applied to a residential building, whose heating system is controlled by means of a model predictive control algorithm. The building model is developed on the basis of the experimental data collected in the framework of a European Commission supported H2020 research project Sim4Blocks, which deals with the implementation of demand response in building clusters. The optimal control problem has been investigated by means of mixed-integer linear programming approach. Real time prices are considered as external signals from the grid driving the DR actions. Results show that the proposed indicators, presented in the form of daily performance maps, allow to effectively assess the energy flexibility potential through its main dimensions and can be easily used either by an end-user or a grid-operator perspective to identify day by day the best DR action to be implemented

Effect of thiosulfate on pitting corrosion of Ni-Cr-Fe alloys in chloride solutions

Pitting corrosion of Alloys 600, 690, and 800 (UNS N06600, N06690, and N08800) was studied in 1 M NaCl solution with different concentrations of thiosulfate (S2O2 3 −). Alloys exhibited vastly different electrochemical behavior, depending on the S2O2 3 − concentration and chromium content of the alloy. Alloy 600 exhibited a breakdown and repassivation potential that decreased with decreasing S2O2 3 − concentration, in the range from 1 M to 10−4 M. Breakdown and repassivation potentials decreased about 300 mV and 600 mV, respectively, when 10−4 M S2O2 3 − was added to a 1 M NaCl solution. For Alloys 690 and 800, additions of S2O2 3 − in the range of 1 M to 0.01 M caused a decrease in the breakdown and repassivation potentials. Dilute solutions were more aggressive, and a 0.01 M addition of S2O2 3 − to a 1 M NaCl solution caused a decrease in breakdown and repassivation potentials of about 300 mV. In a solution containing 0.001 M Na2S2O3 + 1 M NaCl, Alloys 690 and 800 showed two different submodes of pitting, each one of them existing at a different range of potential. Chloride pitting corrosion was observed at high potentials and was characterized by pits with a lacy cover. The stable pit initiation potential associated with this process in both alloys was near 300 mVAg/AgCl and was preceded by frequent metastable events. Chloride plus S2O2 3 − pitting was observed at low potentials (near −225 mVAg/AgCl) and was characterized by hemispherical pits. In potentiodynamic curves, this submode of pitting showed a characteristic anodic peak of approximately 120 mV width and a maximum current density of 10 μA/cm2 for both alloys. Potentiostatic tests at potentials within this anodic peak led to stable pit growth. Those pits could be repassivated by scanning the potential either in noble or active directions. Low-potential and high-potential pitting submodes were separated by a stable passivity range, as determined by potentiodynamic curves. Upon a further decrease in S2O2 3 − concentration down to 10−4 M, only high-potential pitting corrosion was observed, with pitting and repassivation potentials similar than those in 1 M NaCl solution.Fil: Becerra Araneda, Abraham Alexis. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kappes, Mariano Alberto. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rodríguez, Martín Alejandro. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Carranza, Ricardo Mario. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Comisión Nacional de Energía Atómica; Argentin