La Ventajola housing development

La Ventajola is located in the La Cerdanya area of the province of Girona, very close to the La Molina ski resort. The whole area is of high environmental and scenic value.

Because of the nearby ski resorts, most of the homes are occupied during holiday seasons and at weekends.

Environmental protection and the preservation of traditional high-mountain construction shape every building and planning project in the villages of the area.

Project basis

The La Ventajola development is a group of 13 luxury detached homes with a total heated floor area of 1,636 m2, mainly for holiday use during the ski season and in summer.

The homes are built to a very high standard, above the average requirements of the Spanish Technical Building Code (CTE), with environmentally friendly and technologically advanced solutions.

Because of precedents in the area and the ease of drilling in the sedimentary ground, a geothermal system was chosen as the energy source, with central generation and distribution to each home. This allows comfortable conditions to be reached quickly when the homes are occupied, while keeping the interiors at suitable temperatures during the week using the installed underfloor heating system.

Heating system used

For this installation, a geothermal system was chosen, using ROBUR absorption-cycle gas heat pumps to make use of the heat extracted from the ground.

The absorption thermodynamic cycle can produce hot water at very high efficiency and temperature. In this type of heat pump, 40.9 % of the energy obtained comes from the ground, and its overall heating efficiency is 170 % of the primary energy consumed.

The high efficiency comes from adding the renewable geothermal heat to the heat generated by gas combustion and water condensation.

Description of the energy solution

ROBUR gas heat pumps produce hot water at 65 ºC, needing very little support from condensing boilers for DHW generation. Being able to produce water at a higher temperature than conventional electric heat pumps makes the best use of geothermal energy at times of peak demand.

Back-up from condensing boilers to cover peak demand or the DHW service in summer is guaranteed by compact, integrated systems.

For the geothermal system, 11 boreholes of 80 metres were drilled, 50 % fewer than would be needed with electric ground-source heat pumps.

The distribution ring, a closed circuit, carries the hot water for heating and DHW to a heat exchanger in each home, running through the basement of each house.

The control system allows almost all the heating and DHW in winter and the DHW in summer to come from the geothermal source and the heat recovered from the ROBUR gas heat pumps.

Advantages for developers and users

• Fewer geothermal boreholes, which reduces the investment.
• A high renewable energy contribution: 40.9 % of the energy comes from the ground.
• A simpler installation with a renewable alternative to the solar installation required by CTE HE-4 for DHW production, which is hard to integrate into the traditional buildings of the area.
• A very competitive cost for the whole project compared with other conventional geothermal systems.
• Maximum use of geothermal energy despite the homes not being permanently occupied, even in summer.
• A very significant reduction in energy costs thanks to the extremely high energy efficiency of ROBUR geothermal gas heat pumps.
• Better preservation of the buildings and their contents, which are not subjected to the expansion and contraction caused by temperature differences between weekdays and weekends.
• Low pollutant and CO₂ emissions. A propane-driven geothermal system with a low carbon footprint.
• Very attractive operating costs for end users.