Dutch payback extended
Dutch payback extended
The Dutch Public Building Agency, Rijksgebouwendienst, has introduced new rules that allow up to 15 years to pay back energy-efficiency measures in its buildings. In doing so, the agency has greatly increased the number of cost-effective applications for fluorescent electronic ballasts within the 6 million m^2 that they control.
The Dutch Building Agency is a state-owned organization that manages public buildings in the Netherlands, such as buildings for ministries and public administration, museums, prisons, and some educational facilities. The agency controls about 5 000 buildings.
In 1990, the agency introduced a plan that aims at reducing the total annual energy use of 3 080 GWh (billion kWh) in its buildings by 20 percent by the year 2000. The plan followed the Dutch government's decision to launch a national environmental plan, which, among other things, calls for a 20% reduction in national energy demand by the year 2000 (see IAEEL Newsletter 1/92, and 1/93).
However, since the agency had been successful in energy management up to 1990 (between 1977 and 1990, the energy use for heating was reduced by 23%), the normal pay-back applied at that time-a maximum of 6 years at ~7% discount rate-meant that it would be hard to meet the 20% goal on its premises. Thus, the agency decided to allow investments with up to a 15-year payback.
Says Mr. Aard Korbee at the agency: "This does not mean that all or even most investments require that long a payback period. But now we can let very profitable investments pay for less profitable ones." The total lighting load in the agency's buildings is estimated at 66 MW. The aim is to reduce the load by 17 %, down to 55 MW by the year 2000. The present average lighting load for the whole building stock is 11W/m^2, which will be reduced to ~9.2 W/m^2. (If office rooms are considered separately, the present average load is ~14 W/m^2, which will be reduced to ~11W/m^2.)
"We are considering control technologies that would achieve even greater savings. In office rooms, the average lighting load could be reduced by another 25%", Mr. Korbee says.
Emphasis will be placed on installing a combination of light sensors and dimmers that would automatically compensate for lamp lumen depreciation. Thus, initial lighting levels when fluorescent tubes are new would be reduced substantially. These control technologies would also reduce lighting energy use when daylight is abundant. Occupancy sensors are presently not being seriously considered owing to previous experience with poor reliability and problems in combining the two strategies at a reasonable cost. The payback for installing the dimming technologies described above is estimated at between 2.5 and 6 years, depending on the number of hours per year that the room is used, and the number of luminaires that can be controlled by one system.
Nils Borg