Open Access
Simulation of thermoelectric heat pumps in nearly zero energy buildings: why do all models seem to be right?
(Elsevier, 2021) Martínez Echeverri, Álvaro; Díaz de Garayo, Sergio; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Catalán Ros, Leyre; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
The use of thermoelectric heat pumps for heat, ventilation, and air conditioning in nearly-zero-energy buildings is one of the most promising applications of thermoelectrics. However, simulation works in the literature are predominately based on the simple model, which was proven to exhibit significant deviations from experimental results. Nine modelling techniques have been compared in this work, according to statistical methods based on uncertainty analysis, in terms of predicted coefficient of performance and cooling power. These techniques come from the combination of three simulation models for thermoelectric modules (simple model, improved model, electric analogy) and five methods for implementing the thermoelectric properties. The main conclusion is that there is no statistical difference in the mean values of coefficient of performance and cooling power provided by these modelling techniques under all the scenarios, at 95% level of confidence. However, differences appear in the precision of these results in terms of uncertainty of the confidence intervals. Minimum values of uncertainty are obtained when the thermal resistance ratio approaches 0.1, being ±8% when using temperature-dependent expressions for the thermoelectric properties, ±18% when using Lineykin's method, and ± 25% when using Chen's method. The best combination is that composed of the simple model and temperature-dependent expressions for the thermoelectric properties. Additionally, if low values of resistance ratio are anticipated, empirical expressions from the literature can be used for the thermal resistance of the heat exchangers; for high values, though, experimental tests should be deployed, especially for the heat exchanger on the hot side.
Open Access
Annual energy performance of a thermoelectric heat pump combined with a heat recovery unit to HVAC one passive house dwelling
(Elsevier, 2022) Díaz de Garayo, Sergio; Martínez Echeverri, Álvaro; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
This paper proposes a HVAC system that integrates a thermoelectric heat pump with a double flux ventilation system and a sensible heat recovery unit able to provide heating, cooling and ventilation to a 74.3 m2 Passive House certified dwelling in Pamplona (Spain). This study computationally investigates the energy performance of the system and the comfort conditions of the dwelling for one year long. The thermoelectric HVAC system maintains adequate comfort conditions with an indoor temperature between 20–23 °C in wintertime and 23–25 °C during summer, thanks to the precise control of the voltage supplied to the thermoelectric heat pump that can regulate the heating/cooling capacity from 5 to 100 %. The system consumes 1143.3 kWh/y (15.3 kWh/m2y) of electric energy, that can be provided by 4 photovoltaic panels of 250 Wp each. This system is then compared with a vapor compression heat pump with a COP of 4.5. The vapor compression system reduces the electric energy consumption by 36.1 % with respect to the thermoelectric system, which allows saving only 270 Wp (1–2 PV panels). This demonstrates the promising application of thermoelectricity for HVAC in passive houses.
Open Access
Design and analysis of a two-stage cascade system for heating and hot water production in nearly zero-energy buildings using thermoelectric technology
(MDPI, 2024-12-16) Ordóñez, Javier ; Díaz de Garayo, Sergio; Martínez Echeverri, Álvaro; Algarra Pérez, Fernando; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Gobierno de Navarra / Nafarroako Gobernua
This paper proposes an innovative system that integrates two thermoelectric heat pumps (one air–water and the other water–water) with two thermal storage tanks at different temperatures to provide heating and domestic hot water to a 73.3 m2 passive-house-certified dwelling in Pamplona (Spain). The air–water thermoelectric heat pump extracts heat from the ambient air and provides heat to a tank at intermediate temperature, which supplies water to a radiant floor. The water–water heat pump takes heat from this tank and provides heat to the other tank, at higher temperature, which supplies domestic hot water. The system performance and comfort conditions are computationally analyzed during the month of January under the climate of Pamplona and under different European climates. The COP of the system lays between 1.3 and 1.7, depending on the climate, because of the low COP of the air–water thermoelectric heat pump. However, it is able to provide water for the radiant floor and to maintain the temperature of the dwelling above 20 °C 99.8% of the time. Moreover, it provides domestic hot water at a temperature above 43 °C 99.9% of the time. Noteworthy is the fact that the water–water heat pump presents a COP close to 4, which opens up the possibilities of working in combination with more efficient heat pumps for the first stage.
Open Access
Optimal combination of an air-to-air thermoelectric heat pump with a heat recovery system to HVAC a passive house dwelling
(Elsevier, 2022) Díaz de Garayo, Sergio; Martínez Echeverri, Álvaro; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
The main objective of this research is to propose a HVAC system for an 80–100 m2 passive house dwelling based on a thermoelectric air-to-air heat pump combined with a heat recovery unit. The computational parametric investigation demonstrates that the integration of the heat recovery unit significantly improves the coefficient of performance of the heat pump: 2–3 times for partial load operation and 12.5 % for maximum load. Moreover, the number of required modules to reach the maximum performance is at least 5 times lower. A second analysis assesses its seasonal heating performance in three climates as stated by the energy labeling Directive 2010/30/EU. The optimum number of thermoelectric modules in all cases is close to 15, regardless of the climate. This 15-modules thermoelectric heat pump provides a maximum heating capacity of 2500 W and 405 W for cooling, which compensates the typical internal heat gains and the transmission heat flux through the building envelope and the ventilation in the passive house dwelling. Finally, the analysis reveals that, in order to increase this cooling capacity, it is more convenient the improvement of the heat exchangers between the thermoelectric modules and the cooling air stream, rather than increasing the number of modules.
Open Access
Thermoelectric heating and air conditioning with double flux ventilation in passive houses
(2022) Díaz de Garayo, Sergio; Astrain Ulibarrena, David; Martínez Echeverri, Álvaro; Ingeniería; Ingeniaritza; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua
Esta tesis propone el uso de bombas de calor basadas en termoelectricidad, cuyas ventajas competitivas se basan fundamentalmente en la ausencia de partes móviles y de refrigerantes. Concretamente, esta tesis se centra en el diseño y construcción de un dispositivo de bomba de calor air-aire integrado con la ventilación de doble flujo en viviendas con una superficie inferior a 100 m2 y una envolvente de alta eficiencia energética tipo ‘Passive House’, donde la reducida carga de calefacción (<10 W/m2) permite climatizar el espacio con el caudal de aire de ventilación, aprovechando el calor residual del aire renovado. Los resultados demuestran que la termolectricidad puede resultar una alternativa real a la construcción de bombas de calor para la climatización de viviendas ‘Passive House’, dada la gran cantidad de ventajas (sistema silencioso, robusto, diseño ligero y fácilmente instalable en techos falsos, fácil regulación, integrabilidad con instalaciones fotovoltaicas y potencial de ahorro en los costes de fabricación), comparado con su menor eficiencia, fácilmente compensable con el incremento de la producción fotovoltaica integrada en el edificio.
Open Access
Prototype of an air to air thermoelectric heat pump integrated with a double flux mechanical ventilation system for passive houses
(Elsevier, 2021) Díaz de Garayo, Sergio; Martínez Echeverri, Álvaro; Aranguren Garacochea, Patricia; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
This paper describes the design of an air-to-air thermoelectric heat pump for its integration with a double flux mechanical ventilation system for domestic use in Passive House standard. The prototype has been built and thermally characterized in a test bench reproducing winter and summer conditions, with different gaps between indoor and outdoor temperatures. In addition, two different integration possibilities have been analyzed and tested: a stand-alone installation and the combination with a heat recovery unit. This prototype is composed of 10 thermoelectric modules and finned heat pipes to transfer the heat between the modules and the incoming and outgoing ventilation flows. The maximum heating capacity with 12 V supply was proven to be 1,250 W for heating and 375 W for cooling, with COPs ranging 1.5–4 and 0.5–2.5 respectively. Results show the variations in the performance of the thermoelectric heat pump depending on the voltage supply (3–12 V), the air flows (55–130 m3/h) and the temperature gaps between them. This paper demonstrates the convenience of combining passive and active heat recovery technologies (thermoelectric pump coupled to a heat recovery unit), bringing improvements on the thermal power higher than 25% for heating and 10% for cooling, with respect to the thermoelectric heat pump working directly between the incoming and outgoing air flows. The COP is also increased, especially for low energy demands, when the voltage is 3–6 V. In these cases, the COP might be improved by 50% for heating and 30% for cooling.