Porsche showroom and service building in Bucharest

The PORSCHE centre Bucharest West 2 comprising car showrooms and service facilities with a floor area of 3.507 m² was inaugurated in August 2006. The HVAC system, designed to cover the heating load (308 kW), cooling load (313 kW), ventilation load and domestic hot water production (200 kWh/day), is based on reversible heat pumps using 128 vertical borehole heat exchangers of 70 m depth each as heat source. The results of the first monitoring period (2006-2007) show that energy input was 5 times less, CO₂ emmissons were 10 times less and heating costs 3 times less compared to a conventional HVAC system.

Project description

Building, overall energy concept

The PORSCHE centre Bucharest West 2 comprising car showrooms and service facilities was inaugurated in August 2006 . The building construction, with a total unfolded area of 3.507 m², is metallic, structured in four distinctive parts, namely:
- a showroom of 360 m², made of steel and glass,
- a showroom of 795 m², from which 650 m² represent the area of car presentation, with glass surfaces on 3 sides and with metallic curved roof, and 145 m² represent the office area, on two levels with panoramic view to the showroom at the ground floor,
- a middle section made of metal and glass (421 m²), that links the metallic constructions of the two showrooms with a public destination room, having the role of coffee place, including an auto parts shop, services of invoicing and payments, sanitary and two distinctive areas for new car delivery with glass pliable sectional gates,
- an assembly room of 1.931 m², with thermally insulated lateral walls, with concrete struts and ribs, and a "sandwich" roof made of light materials comprising the following divisions: auto mechanics shop, car washing and cleaning, warehouse for spare parts, car reception and diagnosis, and social area.

According to the specific climatic conditions of the capital of Romania and to the imposed indoor temperatures the following calculation data were set up:

Winter situation:

- outdoor air temperature: -15°C
- outdoor air relative humidity: 80%
- indoor air temperature for public areas, showrooms, offices and sanitary facilities: 20°C
- indoor air temperature for production areas: 18°C

Summer situation:

- outdoor air temperature: 34,5°C
- outdoor air relative humidity: 11,95%
- insurance degree: 98%
- indoor air temperature for public spaces, showrooms, offices and sanitary facilities: 26°C
- indoor air temperature in production spaces and in the warehouse: 27°C

The thermal loads resulting from the calculation are as follows:

- heating load during winter time: 308 kW
- cooling load during summer time: 313 kW
- domestic hot water preparation: 200 kWh/day

Heat pump system

The HVAC system was designed and implemented by ASA Holding SA, in collaboration with IMSAT Muntenia SA as general building equipment entrepreneur. It is designed to cover the heating load, cooling load, ventilation load and domestic hot water production and is based on nine reversible ground source heat pumps.

The heat source system consists of 128 vertical borehole heat exchangers of 70 m depth each which were installed on an area of 3.500 m², in order to ensure a energy exchange with the ground of 475 MWh for heating (including the domestic hot water) and of 393 MWh for cooling (see Figure 1).

A floor heating system with more than 750 m² was installed in the show rooms and the public area for clients. The underfloor piping systems are made of high density polyethylene, buried in cement capping and regularly placed near the glass walls. These systems are supplied by the 17 water-to-water heat pumps in wintertime with heating water and in summertime by cooling water.

Eight reversible water-to-air heat pumps are connected to ventilation channels mainly located in the false ceilings of the building. They are mixing the fresh air with the re-circulated air and function on the "auto change over" principle, meaning they switch automatically from heating mode to cooling mode, as a reaction to "building overheating".

All water-to-water and air-to-water heat pumps are manufactured by Florida Heat Pump (Ft. Lauderdale, USA) and use R410A as refrigerant.

Operation experiences

For the time period under survey (October 2006 - April 2007) the Coefficient of Performance (COP) of the HVAC system was always higher value 4,8. That means a SPF>4,8 (see Figure 2).

Costs, economic efficiency, incentives

The average value of the specific effective electric energy consumption for the winter period (October 2006 - April 2007) was 6,83 kWh/(m² x month). For an average price of the electric energy of 72,86 Euro/MWh (exclusive VAT and excises) the operating cost of the geothermal system during winter for a total of 47,8 kWh/(m² x year) is 3,48 Euro/(m² x year).

Regulations, guidelines, benchmarking

The implemented quality management system is based on standard ISO 9001/2000 and was awarded by SRAC and IQNet in 2004.

The sum of the values of the monthly specific thermal energy consumption during winter amounts to 112,32 kWh/(m² x year). According to law 372/2005 regarding the energy performance of buildings (Directive 91/2002/CE), the value of 112,32 kWh/( m² x year), corresponding to class B of the energy classification scale for buildings in Romania, was correctly anticipated by the calculation of the global coefficient of thermal insulation and corresponds to the present demands imposed to the new and mechanically ventilated industrial buildings.

References

More technical information and contact details are to be found in the following project report :

PORSCHE Bucharest West 2 - An example of earth energy complex valorization. Polizu, R. (Romanian Geoexchange Society); Gavriliuc, R. (T.U. of Civil Engineering Bucharest)

¹ Monitoring period: October 13, 2006 - April 10, 2007
² heat load
³ cooling load
⁴ 200 kWth per day for domestic hot water preparation