Energy flexibility potential of domestic hot water systems in apartment buildings

Åse Lekang Sørensen,Inger Andresen,Harald Taxt Walnum,Igor Sartori,J Kurnitski,M Thalfeldt

doi:10.1051/e3sconf/202124611005

Åse Lekang Sørensen, Inger Andresen + Show 4 more

Open Access

https://doi.org/10.1051/e3sconf/202124611005

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Abstract

Domestic Hot Water (DHW) storage tanks are identified as a main source of flexible energy use in buildings. As a basis for energy management in apartment buildings, this paper describes the aggregated DHW use in a case building, and analyses the potential for DHW energy flexibility by simulating different control options. The case study for the work is an apartment building in Oslo with 56 apartments and a shared DHW system. Energy measurements are available for consumed hot water, hot water circulation, and energy supplied to the DHW tanks. The measurements are presented with minute, hourly and daily values. Aggregated daily energy use for the consumed hot water is in average 362 kWh, while the energy supplied is 555 kWh. The potential for energy flexibility is analysed for a base case and for four different rule-based control options: Power limitation, Spot price savings, Flexibility sale and Solar energy. Economic consequences of the control options are compared. With the Norwegian tariff structure, maximum hourly power use has the main impact on the cost. Control systems that aim to reduce the maximum power use may be combined with spot price savings or to offer end-user flexibility services to the grid.

Highlights

1.1 Flexibility potential of Domestic Hot Water (DHW) systemsMoving towards zero emission buildings and neighbourhoods, thermal and electric energy loads can be managed in a flexible way to achieve i.e. reduced power peaks, reduced energy use, reduced CO2emissions, and increased self-consumption of locally produced energy
The flexibility capacity of DHW systems is largely based on the volume of the storage tank [1]
The results show reductions in electricity use during the disconnections, and indicate a risk for new system peaks if several DHW tanks are reconnected all at once. [7] analysed the stochastic nature of DHW demand in residential houses, used machine learning to predict the behaviour in 6 individual houses, and investigated the potential for energy reduction by an adapting hot water system. [8] analysed DHW consumption profiles from 95 residential houses and aggregated information

Summary

Introduction

1.1 Flexibility potential of DHW systemsMoving towards zero emission buildings and neighbourhoods, thermal and electric energy loads can be managed in a flexible way to achieve i.e. reduced power peaks, reduced energy use, reduced CO2emissions, and increased self-consumption of locally produced energy. Domestic Hot Water (DHW) storage tanks are identified as a main source of flexible energy use in buildings [1]. As buildings are becoming more energy efficient, the share of DHW energy is increasing. With demand side management (DSM) it is possible to influence the end-use of energy in a number of ways, by reducing (peak shaving), increasing (valley filling) or rescheduling (load shifting) the energy demand [3]. For the DHW system, load shifting of the energy profile is possible, i.e. by preheating the storage tanks or delaying the heating of the hot water. When storing DHW there are heat losses; [2] found ranges from 2% to 36% heat losses in the storage tanks depending on the system solution. The VarmtVann2030 project found annual heat loss values in the range of 4 kWh per litre stored [4]

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