District cooling in Helsingborg, Sweden

In 2017, Öresundskraft started to expand their current district cooling grid by installing an absorption chiller at Västhamnsverket in Helsingborg to deliver more cooling and replace individual electrical chillers with district cooling.

By utilizing sea water and waste heat for cold production, emissions as well as electrical consumptions have been cut by 65-70%.

Description

Öresundskraft is a publically owned energy company in the southern part of Sweden. The company provides district heating and cooling to apartments and commercial buildings in the city of Helsingborg (about 110 000 inhabitants) by utilizing waste heat mainly from the waste-fired power plant Filbornaverket. In 2017 Öresundskraft started to expand its current district cooling grid by installing an absorption chiller at Västhamnsverket in Helsingborg to deliver more cooling and thereby replace individual (electrical) chillers with district cooling.

Öresundskraft began its district cooling operation in 1999 and since the demand has grown steadily. Helsingborg has especially found an increased cooling demand from offices and commercial buildings. To meet the increasing demand Öresundskraft decided to invest € 2.93M in an expansion of the current district cooling system and a modernization of production facilities. It was expected, that the fully implemented district heating system would reduce both electricity consumption and environmental emission between 65 and 70%, compared to traditional and individual cooling systems.

Absorption chillers are primarily powered by heat and not by electricity. Adsorption cooling is a cost-effective and environmentally friendly technology for producing cold. It is suitable for cities with high electrical prices and plenty of available cheap waste heat. Considering that summertime peak electric demand is largely driven, in southern Europe especially, by cooling, the advantage in the development of these systems is also in terms of shaving electric energy demand peaks. To implement this type of system the amount and temperature of available waste heat should be considered, preferably the temperature of the heat is at least 90 °C all year long.

Another advantage with district cooling compared to other technical solutions for cooling (e.g. individual chillers) is that the amount of cold provided to the end user can relatively easily be increased if the demand increases. Besides that, district cooling is also a well-known technic and the system requires low work effort and maintenance [1].

Efficient

The absorption chiller commissioned in 2017 utilizes about 8 MW of district heating and has an efficiency of approximately 60 %. The overall production of district cooling from the absorption machine is typically 4 MW to 5 MW. Within the project, necessary arrangements were made to capacitate the installation of a second absorption chiller in the future.

The idea, the system and the technical requirements

Besides a new absorption chiller, the project also included the installation of a seawater collection tank to provide free cooling to the machine. The new tank was installed in the spring of 2018 for the supply and distribution of seawater. The new installation was in place at the end of June of 2018 and in July the production of district cooling in Helsingborg increased by 214 % compared to the same month the year before, i.e. the production increased from 1686 MWh to 3620 MWh.

The district cooling plant utilities free cooling from the sea by first pumping the water into the tank and then filtering it before passing through a heat exchanger system, i.e. a plate and frame heat exchanger of titanium, to cool the cooling distribution system. Within the system, seawater cooling can either be used for “free cooling” (in winter) or for cooling the absorption machine (condenser and absorption) while it simultaneously also pre-cools the warm district cooling return water, before the absorption chiller.

The system is designed such that free cooling from the sea provide cold directly to the network until the temperature of the sea is too high. At that time the absorption machine is started. As the cooling demand is usually higher in summer than during winter and the heating demand is lower during summer the absorption machine utilizes excess capacity in the district heating network to produce cold for the local offices and buildings.

In summer, the district heating network’s heat source is a waste-fired boiler, that needs to be operated to take care of the waste, despite the low heat demand. Waste is difficult to store from summer to winter, without undesired biological activity. The combination with cheap excess heat and a heat-driven chiller is most beneficial in systems where a significant fraction of heat is provided by industrial heat recovery systems, waste incineration or cogeneration plants that produce large amounts of heat also during the summer period.

In Helsingborg, the total amount of waste heat is about 50 GWh. Even with the new installation, there are still some waste heat that is cooled off using a large dry-cooler or free cooling. To utilize the waste heat even more efficiently, Öresundskraft is considering installing a second absorption chiller and/or a geo-energy seasonal storage.

Operational experience

 Figure 1. District cooling by the sea. Source: Mutaz Alkiswani, Öresundskraft

 Figure 2. Magnification of figure 2. Source: Mutaz Alkiswani, Öresundskraft

The temperature of the sea usually has small variations, and the seasonal variations were in this case managed by adjusting the size of the system to suit the highest predictable temperature. At high temperatures the amount of seawater required to cool the process increases, therefore the water flow can be adjusted. Besides that, there are also two control valves on the cooling system to adjust for variations and stabilise the system.

The unpredictably high seawater temperatures during the summer of 2018 resulted in a little lower cooling efficiency of the absorption chiller. This did not affect the performance of the machine, but it made it difficult to pre-cool the district heating return flow. To prevent this from happening again the size of the system for cooling down the district heating return flow was increased at the end of the testing period.

Helsingborg, Sweden

ReUseHeat

Construction is to begin during the fall and winter of 2017/2018.

IVL Swedish Environmental Research Institute

Names of stakeholders

Jesper Baaring (Öresundskraft)

Öresundskraft AB

Related Celsius content:

Connecting municipalities, Excess heat from datacentre in Val d’Europe, France, Open District Heating in Stockholm, Sweden

External links:

4 fördelar med fjärrkyla, Filbornaverket, Västhamnsverket, Öresundskraft AB, Handbook – 25 cases of urban waste heat recovery