Photovoltaic diesel cooling-system technology for transport vehicles
involved in temperature-controlled logistics

Technology demonstration – hybrid refrigerated truck systems

Since 2014, researchers at the DLR Institute of Networked Energy Systems have been working intensively on a concept for mobile photovoltaic systems in the field of temperature-led logistics. A market analysis of the logistics sector was carried out as part of a master’s thesis, among other research, with a view to assessing the potential pertinence and marketability of such technology. This revealed strong relevance to new innovations aimed at reducing energy consumption, and the willingness of companies to opt for greener logistics. Visible efforts to reduce CO 2 can help to win customers over the competition and have a positive impact on a company’s image.

A new yield prognosis model has been created to estimate the savings that could potentially be achieved by opting for photovoltaic-based refrigeration systems for goods transport. This can be used to predict the average annual energy yield for every existing transport route when using the mobile PV system. The calculated results are based on real telemetric data and show that, for routes within Europe, approx. 1000–2000 litres of diesel fuel can be saved every year by using such a refrigeration unit. This equates to a saving of around 30–40% diesel for refrigerated goods.

Feeding photovoltaic energy into the existing refrigeration system is key to the feasibility of the concept. This was analysed with the help of a new model to illustrate refrigeration units, taking all possible disturbances into account. One key finding was the identification of an optimised regulatory structure. This enables the integration of an optimum amount of photovoltaic energy in both economic and environmental terms, without the use of additional intermediate electrochemical storage (batteries).

The findings suggest a dual setpoint control, which the DLR Institute of Networked Energy Systems has secured in the form of a patent application. The operating principle is as follows: with suffciently high electrical power provided by the photovoltaic system, the system-cooling function is regulated at a lower temperature setpoint. The energy obtained via this method is stored in cold form and has the advantage of allowing the user to dispense with conventional battery storage, which is expensive and high-maintenance.

German Aerospace Center (DLR)
Martin Vehse · E-Mail: martin.vehse@dlr.de · DLR.de/en