ENERPOS / La Réunion
Géolocalisation : Latitude
Longitude
South
West
21° 20'
55° 29'
BUILDING FEATURES
NET ZERO ENERGY BUILDING
Building Owner : University of La Reunion Type of building : Classrooms,offices Includes : 7 classrooms, 7 offices, 1 meeting room, car park, planted patio Employees/Occupants : Thirteen staff members (administration, teachers...), students Number of Storeys : 2 Gross Floor Area : 1,425 m² Air-Conditioned Space : 246 m² Spaces with Natural Ventilation & Ceiling Fans Only :
In the French tropical regions, nonresidential buildings are often badly designed with no respect to basic bioclimatic principles. ENERPOS (which stands for Positive Energy in French) is the first educational net-zero energy building in the tropics and one of the 13 Net ZEBs in the tropics thanks to its bioclimatic design. Building an energy efficient building in such a climate is particularly challenging. However, the energy expectations with regard to ENERPOS have been reached, even largely exceeded : in terms of energy use, it consumes one seventh of the average for university buildings in Reunion Island and produces seven times its consumption by BIPV (Building Integrated Photovoltaic) roofs. The French Agency for Environment and Demand Side Management (ADEME) and the Regional Council of La Reunion funded extensive metering that measures energy by end use and PV production. The building is not only an energy-efficient building, but also displays various passive methods to reduce energy consumption while providing a comfortable environment for its users. It has been designed with priority given to the passive components such as cross natural ventilation and solar shading.
435 m² Total Net Floor Area :
CLIMAT ANALYSIS
681 m² Performance Standards : _PERENE 2004 _ HQE Total Cost : $1.7 million Cost Per m² : $1110 (gross/ floor area) $2320 (net floor area) Substantial Completion : August 2008 Occupancy : 2009
ENERPOS is located in Saint Pierre on the French island of La Reunion. This island, whose tropical climate is hot and humid, is located in the Indian Ocean. This area is also often struck by tropical cyclones, generating building difficulties. The climatic conditions (Temperatures and Sun rays) of Saint-Pierre are listed in the Table. The prevailing winds blow from the east and south-east - the west coast being known as the leeward coast. The energy situation is complicated because La Reunion is very a small island. The production of electricity is limited, and the island aims to have energy independence by 2030.
CLIMATOLOGICAL INDEX CARD ST PIERRE'S URBAN AREA
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BUILDING TEAM
SITE INTEGRATION
Architect :
According to the architect's wishes, the building was built in accordance with the existing ground. The immediate surroundings have been designed with respect to the site integration. ENERPOS is a two-storey building composed of two parallel blocks with a green patio in between. The two building wings are orientated to be exposed to the summer thermal breezes and to reduce the solar energy gained on the western and eastern façades.
Thierry Faessel-Boehe General Contractor : Léon Grosse Mechanical Engineer : INSET Energy Modeler : PIMENT Lab & Imageen Lighting Design : Imageen Structural, Civil Engineer : RTI Environmental Consultant : TRIBU Paris BUILDING ENVELOPE
PASSIVE APPROACHES
ROOF Type : BIPV over-roof + 10 cm (3.9 in.) of polystyrene + 20 cm (7.9 in.) concrete Overall R-value 3.4/Solar factor: 0.003
The energy consumption of a building relies on the way it has been built… ENERPOS uses many passive techniques (design measures that require no direct purchased energy input). For example, the building is naturally cross ventilated with a window to wall ratio (WWR) of 30% by using glass louvers. Main facades are solar protected with wooden strips. Daylight is the primary light source for the classrooms and offices. The building is also surrounded by native plants to prevent the air from heating up before entering the building.
WALLS Type :
SECTION
East and West: 18 cm (7.1 in.) concrete + 8 cm (3.1 in.) mineral wool or 18 cm (7.1 in.) concrete + ventilated air gap + wooden siding North and South: 18 cm (7.1 in.) concrete + solar shading
LEGEND 1. Building orientation : main facades are north-south orientated to ventilate thanks to the thermal breeezes 2. Building Integrated Photovoltaic over-roof (365m² - 50kWp) 3. Insulated roof : 10 cm of polystyrene. Solar factor of the roof = 0.003 4. Outside louvers – WWR = 30 % 5. Cross natural ventilation 6. Outside walkways 7. Vegetalisation of the surroundings 8. Fixed solar shading – horizontal wooden strips. Solar factor of the walls = 0.03
Overall R-value E and W: 1.8/S-value: 0.02 N and S : 0.1/S-value: 0.03 Glazing Percentage 30% WINDOWS U-value 1.4 Solar Heat Gain Coefficient (SHGC)
GROUND LEVEL LAYOUT
SITE PLAN
N: 0.10 - S: 0.15 Visual Transmittance : 0,4 BUILDING MATERIALS Structural material : Concrete Solar shading systems: Wooden strips Roof: Photovoltaic roof insulated with polystyrene
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ENERGY SYSTEMS
ENERGY EFFICIENCY SYSTEMS
Cooling system :
Energy management strategies are used to decrease the total consumption of the active systems. The installed electric density for artificial lighting is lower than in a standard building. Low energy T-5 luminaires provide indirect ambiance lighting, while LED desk lamps in the offices provide additional lighting. Timers in the classrooms turn the lights off automatically after two hours. Large ceiling fans are used in conjunction with the natural ventilation strategy to create air movement on the skin of the occupants. They guarantees additional air speed during windless days andallows a transitional period before using active air-conditioning systems. A variable refrigerant flow (VRF) airconditioning system is installed to cool the offices and the computer rooms. A building management system controls the air-conditioning system and energy consumption by type of end uses. To reduce plug load energy consumption, the use of laptops and nettops is encouraged in the offices.
Desklamp:
SW :
E N E R G Y FEATURES Annual Energy Use Intensity (EUI) (Site) : 14.4 kWh/m² net floor area Electricity (From Grid) : 14.4 kWh/m² .area Annual Source Energy : 47.5 kWh/m².area Conversion Factor Primary/Final Energy : 3.3 Annual On-Site Renewable Energy (PV) Exported :
RENEWABLE ENERGY SYSTEMS The very low consumption of the building is balanced by 350 m² of building-integrated photovoltaic roofs. The PV panels serve as overroofs, with half oriented north and half oriented south. The slope of the PV cells is 9° for both roofs. Besides electricity production, the PV panels provide a ventilated double roof, which creates solar shading of the terrace roof of the building. Because of the PV layer, the solar factor of the roof is 0.003 whereas the PERENE requirement is 0.02. The underlying philosophy of ENERPOS is to balance the final energy consumption of all its uses with its PV production and to reduce the stretch of time until the energy balance is reached. The advantage of a tropical climate is that the peak energy consumption occur simultaneously.
104.4 kWh/m².area E N E R G Y END USED
ENERGY ANALYSIS
Fifteen electricity submeters monitor various loads and archive data
Energy Demand (kWh/m².year)
Energy Supply (kWh/m².year)
Plug Loads
Electricity Final: Primary:
Renewable Energy Final: Primary:
46% Air Conditioning + Mechanical Ventilation 15% Interior Lighting : 14% Ceiling Fans : 11% Exterior Lighting : 7% Elevator : 7%
16 52
115 380
Final Energy Demand is the sum of all delivered energy obtained by summing all energy carriers. Final Energy Supply is the sum of all energy generated on site from renewable sources. The Primary Energy Demand and Primary Energy Credit have been calculated based upon the Primary Energy Conversion Factors for each energy carrier for this location.
Annual Energy Balance According to PERENE, a university building has an energy index of 140 kWh/m² •yr. ENERPOS consumes one-tenth the energy of a standard building. The EUI for this year was 14.4 kWh/m²•yr. The Figure represents the consumptions month-by-month for all of the end uses. The plug load consumption remains more or less constant over the year. The consumptions that vary the most are the air conditioning, ceiling fans and interior lighting.
MONTHLY ENERGY USE, MAY 2010–APRIL 2011
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KEY SUSTAINABLE FEATURES Vegetation : A 3 m (9.8 ft) band of native plants around the building helps prevent the surrounding air from heating up. Native plants have low water needs and are adapted to cyclones. Natural ventilation and celling fans Cross Natural Ventilation : (window to wall ratio: 30%). Indoor Louvers : Between the offices and the central corridor.
POE THERMAL CONFORT To assess the comfort level of ENERPOS, a postoccupancy evaluation was conducted during three hot seasons (October to April). It involved surveying students and lecturers during the hours of occupancy. Students were asked to complete a questionnaire at the same time that the environment parameters were being recorded (air temperature, wet-bulb temperature, globe temperature, relative humidity and air velocity). More than 2,000 questionnaires were filled in by 600 students and their teachers. The main results are that the occupants usually don’t complain about the heat and generally feel comfortable, even during the hottest period of the year.
Ceiling Fans : one per 10 m² (all spaces)
LESSONS LEARNED
Daylighting N-S Façades : solar protected with wooden strips (simulated with 3-D software, optimized for daylighting). Useful Daylight Index of 90% in most spaces. No artificial lighting in two classrooms on the first level facing the sea. Artificial lighting : Offices :
Elevator Energy. Data from the energy monitoring system showed that energy consumption of the elevator accounted for 13% of the overall energy use of the building . All the inside lights were constantly turned on even if the elevator was closed with no one inside. A standby mode was activated, and this measure cut the energy used by the elevator in half.
7 W/m² (255 Btu/ft²)
Air Conditioning and Natural Ventilation. The air conditioning and the air treatment unit are installed in the offices. Using Givoni’s comfort diagram on a psychrometric chart, it was possible to predict the different operational periods for natural ventilation, ceiling fans or air conditioning.
Individual Controls :
Interior Lighting.
Individual controls for office ceiling fans and lighting. Use left at the discretion of occupants. Classroom Controls : Grouped controls for ceiling fans. Timers turn off lighting after two hours
Another improvement could be made on the interior lighting switches of the classrooms. Three parallel areas can be defined: The daylighting is very good near the windows overlooking the exterior, slightly weaker in the middle and even weaker on the side of the building overlooking the green patio.
Building Management System :
Occupant Behavior.
Wall mounted neon tubes (100 Lux) plus 9 W LED desk lamps (300 Lux) = 3.7 W/m² (134 Btu/ft²). Classrooms :
15 energy and power meters; 15 temperature and humidity sensors and presence detectors Water :
The ultimate objective is to get active people in a passive building. To do this, people need to be educated and to adapt their behavior. Signs in classrooms explain how to properly use the building by opening the louvers or turning on ceiling fans, switching off unnecessary lights, and using the stairs, rather than the elevator...
Car park located underneath building to increase soil permeability and prevent flooding. Low-flow toilets. Materials : Chairs made from recycled plastic ; organic painting. Occupant Surveys : More than 2,000 thermal comfort surveys during three summer seasons.
Contact Person : François Garde (francois.garde@univ-reunion.fr)
Website : http://lpbs.univ‐reunion.fr/enerpos
Institution : PIMENT / University
Photos credits : Jérôme Balleydier – 06 / 2015
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