Fundació URV

Solar driven absorption cycle for space heating and cooling

Posted by Unitat from Fundació URVResponsive · Innovative Products and Technologies · Spain

Summary of the technology

The invention relates to a new solar thermally driven system that meets the heating and cooling demands of buildings. The system consists of a reversible absorption cycle which operates as a single effect absorption cycle in the cooling mode and as a heat transformer in the heating mode. Components of both cycles are the same, only the flow direction inside the system changes.
In thermally driven systems, solar thermal collectors convert solar energy into thermal heat which can be used to run a thermally-activated device. Different types of thermally driven systems are available on the market, but among them, absorption systems are the most mature technology and are commercially available.
The thermal collectors mostly used in solar absorption installations are flat plate or evacuated tubes. These thermal collectors produce hot water to drive the absorption machine in summer and produce chilled water. However, the hot water temperature obtained in winter with these solar collectors is too low to directly feed conventional heating systems but also is too low to drive the absorption machine in order to produce a higher temperature water stream to feed the heating system. So, in winter the hot water produced in the thermal collectors is heated up in a boiler before to feed the heating units.
The invention proposes a new reversible solar driven absorption machine that in summer it would work as an absorption chiller, as the machines that we can find on the market today, but in winter it would work as a heat transformer. As heat transformer the absorption machine cycle can be driven with a heat source temperature of 40 °C to produce hot water at 60°C at an ambient temperature of 0°C. Furthermore, the lower the ambient temperature, the lower the activation temperature of the machine and higher the machine heating power. Components of both cycles are the same, only the flow direction inside the system and the connection with external devices changes.
To allow the reversibility of the equipment and its operation in winter a new working pair, ammonia/lithium nitrate, has been selected because no rectifier is required and it does not present problems of refrigerant freezing at low condensing temperatures when the cycle operates as a heat transformer.

Fundació URV
Fundació URV

Description of the technology

To increase the contribution of renewable energies and approaching to near zero buildings, basically there are two mature technologies in the market: the solar photovoltaic systems with the electrical reversible heat pumps and the solar thermal systems with Absorption heat pumps.

Although there are still few solar air-conditioning systems, the first option has gained interest in recent years due to the large price reduction of photovoltaic panels and because the absorption machines really just absorption chillers. To produce hot water for heating in winter, the current absorption machines require very high activation temperatures for the solar panels in winter. Therefore, a boiler is used to increase the temperature.

The invention presented here is a solar driven absorption system for space heating and cooling. Thus, a solar air-conditioning for all the year.

The invention proposes a new reversible solar driven absorption machine that in summer it would work as an absorption chiller, as the machines that we can find on the market today, but in winter it would work as a heat transformer.

Both cycles have the same components consisting of five heat exchangers: an absorber, a generator, a condenser, an evaporator and a solution heat exchanger. The five heat exchangers of the equipment are the same, changing the function they perform. The only difference is that the heat transformer cycle includes two pumps, one pump in the solution circuit and another one in the refrigerant circuit, and only an expansion valve in the solution circuit; while the absorption refrigeration cycle has only one solution pump in the solution circuit and two expansion valves placed in the solution and refrigerant circuits. On the side of the solution circuit, the circuit does not change, only the function of the components. On the refrigerant side there is a double circuit to selected according to the active cycle.

All components of the cycle could be plate heat exchangers using water or glycol solutions as external thermal fluids to provide or dissipate heat in each component. In order to dissipate the heat released in the absorber and the condenser to the environment in the case of the absorption chiller or to provide heat to the evaporator from the environment in the case of the heat transformer, the use of a dry cooler is proposed. In a building, it results difficult to justify the use of a wet cooling tower for maintenance costs and hygienic-health risks.

It would be the first reversible absorption machine on the market able to produce chilled water in summer for the cooling demand of the building and hot water to meet the heating demand in winter.

The operation of the machine as a heat transformer in winter would allow obtaining hot water at 60 ° C from a heat source lower than 45 ° C.

Low temperature heat sources are available in many applications, ranging from waste heat from industrial processes and buildings to geothermal and solar heat source. This technology allows the revaluation of low temperature heat sources to obtain useful heat. Therefore, it has many sectors of application, although a priority sector of application would be for heating of buildings from solar energy.

The provision of heating and cooling from renewable sources of energy is a necessary requirement of meeting the ambitious decarbonisation target. In this context, the new hybrid PV-T collectors has the potential to cover a significant fraction of the heating and cooling demands in domestic settings, which represents the 40% of the energy consumption in the EU, by coupling PV-T collectors to absorption systems. It has been estimated that PV-T systems can cover 60% of the heating demand and more than 50% of the cooling demand of average residential buildings in southern Europe.

The proposed technology would allow the use of thermal energy from PV-T collectors to drive the machine and cover the heating cooling demand of residential buildings in Europe. In countries with a higher demand for heating, the operation of the machine as a heat transformer would allow to reduce the temperature of the PV-T collectors and increase the electricity production.

Another possibility of this technology would be its coupling with a Thermal Energy Storage (TES), allowing to reduce the final temperature of the storage and obtain a greater use of solar energy for heating.

Intellectual property status

Patent already applied for

Patent application number : EP19382476

Where : Europe

Desired business relationship

Technology selling

Patent licensing

Joint ventures

Technology Owner

Fundació URV

Technology Transfer Office

Additional information (attached documents)

Related keywords

  • Building Automation Software
  • Construction Technology
  • Installations related to construction (energy, lighting, …)
  • Energy Technology
  • Energy production, transmission and conversion
  • Cooling technologies
  • Renewable Sources of Energy
  • Solar / Thermal Energy Technology
  • Energy efficiency
  • Smart City
  • Real estate

About Fundació URV

Technology Transfer Office from Spain

The Technology Transfer and Innovation Center (CTTi) meets from the University environment the technological needs and services generated by the productive sectors and administration, through the management of Transfer of Technology and Knowledge, the Intellectual and Intellectual Property management, Technology Watch, Entrepreneurship, and Technology Infrastructures Offer (business incubator).

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