Peltier modules control temperatures in niche products such as wine coolers and camping fridges or are used to precisely temper processes as for example the duplication of DNA sections. Accurate characterization and long term stability of the modules is crucial in order to meet the high reliability requirements especially in critical applications such as in space or medical technology markets. While most of the measurement stations are designed for thermoelectric generators, especially in regard to long term testing, the measurement of peltier modules is rarely described. In this contribution, we show a customized measuring station specifically for the combination of the characterization of peltier modules and their long term stability. With this measurement station, it is possible to determine temperature dependent properties such as the maximum current Imax, the maximum cooling power Image 1, the maximum temperature difference Image 2 and the coefficient of performance (COP) while performing cycling tests in between the characterization measurements. In this setup, both sides consist of water driven heat exchangers with a range of Image 3 to Image 4. The heat flow through the module is measured via two graphite heat flux meters. Thereby, it is possible to completely characterize a peltier module within this measuring system. An error analysis for the measured properties is given as well. In addition to the characterization of the modules, the long-term stability of the modules can be measured not only with static current and temperature but also at cyclical stimulation of temperature or current changes meaning that application-oriented long-term tests are possible.

Caloric cooling systems are potentially more efficient than systems based on vapour compression. Electrocaloric cooling systems use a phase transformation from the paraelectric to the ferroelectric state by applying or removing an electric field to pump heat. Lead scandium tantalate (PST) materials show a first-order phase transition and are one of the most promising candidates for electrocaloric cooling. To model caloric cooling systems, accurate and thermodynamically consistent material models are required. In this study, we use a phenomenological model based on an analytical equation for the specific heat capacity to describe the material behaviour of bulk PST material. This model is fitted to the experimental data, showing a very good agreement. Based on this model, essential material properties such as the adiabatic temperature change and isothermal entropy change of this material can be calculated.

Due to climate change, the need for efficient heat pumps is crucial. Magnetocaloric heat pumps are one of these potentially more efficient candidates. Magnetocaloric heat pumps use solid state refrigerants that exhibit a temperature change when a magnetic field change is applied to them. However, current prototype systems are still too expensive for commercial use, due to the need for large permanent magnets. By improving power density, the size of the magnets and therefore the cost can be reduced. To this date the highest power density was achieved by Maier et al (2020 Commun. Phys. 3 1–6) using the novel magnetocaloric heat pipe concept. In this work we improve on the design by building magnetocaloric heat pipe consisting of seven segments connected by check valves. Both ethanol and methanol were tested as the heat transfer fluids. Using 154 g of Gadolinium temperature differences of up to 11.5 K and cooling powers of 128 W were achieved. This is a significant step forward in both maximum cooling power as well as temperature difference compared to previous devices of this kind. An extraordinarily large working frequency of 14 Hz was achieved for this device, leading to a very high power density with a specific refrigerant capacity s R C P of 15 W kg⁻¹. In this work we also propose a simple lumped parameter model, which can predict the system performance and allows for further optimization of caloric heat pipes.

In this study, we characterize electrocaloric lead scandium tantalate (PST) samples by means of the adiabatic temperature change $\Delta T_{\mathrm{ad}}$ and the dissipative heat $q_{\mathrm{diss}}$ with a direct thermal method. The figure of merit ($FOM$), defined as the ratio between the adiabatic temperature change and the thermal hysteresis, quantifies the losses of the material. Additionally, it is also possible to draw conclusions on the efficiency of a caloric cooling system based on the regenerator or cascaded approach. The maximum adiabatic temperature change of the measured samples results in $\Delta T_{\mathrm{ad},\max }=(1.39\pm 0.02)$ K and the dissipative heat yields $q_{\mathrm{diss}}=(0.39\pm 0.05) \mathrm{J}/(\mathrm{k}\mathrm{g} \mathrm{K})$, resulting in an $FOM=(5.1\pm 0.2)$. The efficiency for an ideal cascaded system is given by ${\eta }_{\mathrm{cas}}=0.56$, and for the ideal regenerator, the efficiency is given by ${\eta }_{\mathrm{reg}}=0.84$. The results demonstrate that the PST material in this study exceeds the maximum $FOM$ in the literature by 34%.