Putting the user in the centre

Optimization of energy use in buildings can be achieved in multiple ways. Often the approach is purely technical: related to the knowledge and expertise that is needed for installation, maintenance and running of the building’s district heating system. However, the scope can be widened outside of the technical field. Techno-economic aspects are relevant, as well as the dynamic effects of smart energy management schemes that are the result of behaviour changes from the end user.

Such optimizing on the end-user side has many advantages. But it is at the same time important to understand that not all types of end-users can be treated alike.

This article is a summary of the content in four other articles in the toolbox regarding end user technology and socio-economic impact of different solutions. The longer articles can be found here:

• Making use of the user
• When everything counts
• Storage, steering and smartness
• A reality check on the end-user perspective

Motivations for optimisation on the end-user side

The load for the district heating (DH) and district cooling (DC) network is defined by the consumption of the end-user. Therefore, the performance of the whole network is dependent on the operation of the end-user side. There are several main benefits from optimising the end-user side:

• Reducing the daily peak means that it is possible to decrease the use of more expensive sources of heat/cooling (e.g. gas and oil-fired boilers, electrical air-cooled chillers).
• Reducing the highest peak over the year reduces the peak to baseload ratio which in turn can lead to one of the following events: The heat/cooling source fleet can be optimised since a lower capacity is required to meet the demand, or the DH/DC can be expanded without adding extra sources of heat/cooling.
• Changing the shape of the load can lead to a higher penetration of low-carbon, low-cost heat/cooling sources because some of these are intermittent.
• By having more control on the end-user side, it is possible to adjust the temperature of the water to increase the efficiency of the heat exchange both at the end-user side and at the heat source end. The latter can in turn increase the efficiency of the heat source.
• Working on the end-user side is a way of involving the occupants who play an important role in the DH/DC network.

Having all these elements in mind, it is clear that the DH/DC network stakeholders can benefit from this; and it is likely that other organisations such as energy services companies or building companies will tap into this potential for money if the DH/DC network scheme leaves it available.

The end-user in the district heating/cooling network

There is a variety of types of end-users that are supplied by DH/DC networks. Out of all the possible ones, this overview is mainly focused on the residential sector with hydronic heating system. Commercial buildings, office buildings and industries have different heating and cooling profiles.

Three different end user scenarios can be identified:

• Single family house
• Housing cooperatives
• Apartment buildings

They differ in the way they are connected to the DH grid (district cooling is unusual in apartments). Single family houses usually have their own heat exchanger while housing cooperations usually have a common heat exchanger that serves a number of houses/apartments in the nearby area or the same apartment building. The heat exchanger is an important control point in the end user heating system (read more). Other components in the hydronic heating system is the secondary or local network and the radiator which transfer the heat from the network to the ambient air in the apartments/rooms. All these components are important to regulate the energy consumption.

Social and economic features at the end-user level

Common for almost all residential buildings is that they share the same heat load pattern daily, weekly and over the year. Daily there is a peak in the mornings and in the afternoon; when the residents prepare for the workday in the morning, and when they return home in the afternoon. Weekly we see the same pattern every workday (Monday – Friday) and a more even consumption pattern during the weekends. Yearly we can observe a higher heating demand in the cold season (November – March).

One big challenge is to reduce the peak load periods to avoid using often expensive peak load production units to keep the cost down and avoid fossil carbon dioxide emissions. Peak load production units are often fuelled by petroleum oil or natural gas. There are several different techniques to reduce peak load by short time energy storage.

Refurbishing potential

 Figure 1. Impact of different energy efficiency measures on residential buildings in Gothenburg.[/caption]

Refurbishing older apartment buildings shows that there is a large potential to reduce energy consumption. Changing windows, improving the insulation of the building envelope and improving the ventilation system can reduce heat consumption by 50 % in cold climates.

End-user engagement

One way to put focus on energy consumption is to engage the end-users in any form. This could be done in some sort of agreement where the DH company is allowed by the owner to regulate the heat exchanger to manage peak load situations. The owner is guaranteed a minimum indoor temperature and the DH company can for a short time cut the energy delivery to minimize peak load in the DH system. The heat stored in the building’s construction keeps the indoor temperature within the stipulated limits. There are also more advanced and automated systems to regulate and optimize the living space area’s temperature related to the time of day, outside temperature and weather forecast.

End user engagement can also be created by visualizing the energy consumption on a panel/screen in the house/apartment or a smartphone app in order to create behavioural changes. This creates an awareness about energy consumption and leads to a decreased demand and a potential incentive for the customer/ end-user to reduce costs.