Westfalen AG is well known as a specialist in the cooling sector and supplier of refrigerants. Many people recognize the striking white horse symbol on a red background with more than 260 petrol station outlets in North-Rhine-Westphalia and Lower Saxony operated by the family owned business in Münster.
With the continuing trend of fuel stations developing additional services, such as small convenience stores, with cafes and food – to-go offers, more and more refrigeration is needed and with it the ability to access valuable waste heat energy for use on site.
In November 2010, our customer (the refrigeration specialist, Michels) installed a DK system for waste heat utilisation in a Westfalen petrol station in Olfen. The DK-Energy Storage Tank provides both: potable hot water and heating water in one single tank. The drinking water is heated to high temperatures in a demand flow principle and as a result there is full legionella protection as no potable water is stored.
DK Kälteanlagen has remained true to its origins for the last 39 years. From the outset it was our aim to produce tailor-made storage tanks with the highest flexibility for our customers. Maximum flexibility is achieved through our own tank production and countless heat exchanger combinations.
The picture on the left shows the twin solutions in a single tank. The heating water flow line is located in two thirds of tank height and a buffer of hot water is stored in the upper part of the tank which is separated from the heating water circuit. The upper part of the tank is heated by the de-superheating energy of the cooling units to temperatures above condensation temperature as a result that potable water can be heated to higher temperatures than the condensing temperature.
Internal heat exchangers are fitted over the total height of the buffer tank. This arrangement will ensure two different water-temperatures in the tank. The result is to store the de–superheat energy in the upper part of the tank.
The following cooling machines are installed in the Westfalen petrol station:
Freezer cell Qo = 1.63 kW Qc = 2.90 kW
Freezer cupboard Qo = 1.12 kW Qc = 2.00 kW
Normal cooling cell Qo = 2.20 kW Qc = 3.20 kW
Total performance Qo = 4.95 kW Qc = 8.10 kW
The heat-recovery for this application is a DK-Energy Storage Tank with a volume of 400 litres. Fitted in the tank are three single-walled heat exchangers (2×22 mm/ 2.5 m² + 1×16 mm/ 0.8 m²). For heating the potable water there is a dedicated internal stainless-steel spiralheat exchanger ¾ inch, measuring 15m in total length. In additional the potable water solution, further waste heat energy is used for heating the staff areas of the petrol station.
Warehouse 39 m2
Personal room 11 m2
Rest rooms 20 m2
Preparation room 13 m2
Total area 83 m2
The cooling specialist Michels, recorded technical data for a five month period following the installation (Nov 2010 till March 2011). The data shows that the energy heat recovery was sufficient to ensure the majority of the heating for the rooms and for the hot water preparation. During this colder than average winter the electrical consumption was 90 kWh for the additional electrical heater back-up use. The 6kW electrical heater was in operation for only 15 hours during the entire winter period.
The recorded data is proven evidence that the DK-Energy Storage Tank is an economic and environmentally friendly solution for similar projects. This measuring data allowed for the Westfalen-petrol station in Olfen/ Germany to remove the connection from the mains gas grid.
