2012-04-10 - An ABB variable speed drive solution has reduced the power consumption of the Valorsul waste-to-energy plant in Portugal by 9 megawatt-hours a day, equivalent to a saving of $320,000 a year at current energy prices. Valorsul processes the waste of Lisbon and much of western Portugal into valuable electrical energy, producing enough electricity to power a city of 150,000 inhabitants.
By ABB Communications
One-fifth of Portugal’s waste is processed and converted into electricity at the Valorsul waste-to-energy plant. Located on the outskirts of Lisbon, the plant recovers the solid waste of 19 municipalities in the capital and western Portugal, and turns it into 50 megawatts of electricity – enough to meet the needs of a large city.
Looking for ways to reduce the energy consumption and CO2 emissions of the plant, Valorsul identified six fans with a high energy saving potential: three induced draft (ID) fans and three secondary air fans.
In waste-to-energy plants, ID fans and secondary air fans are an important part of the combustion process. The latter supply secondary air to the boiler to combust the fuel, and ID fans remove the flue gases as exhaust during combustion. ID fans in particular consume large amounts of electrical energy. The method by which the fans are speed-controlled has, therefore, a major effect on energy consumption and operating costs. Prior to the installation of the ABB solution, the fans were controlled by dampers, which is the least energy-efficient control method available.
By replacing the dampers with an ABB variable speed drive solution, Valorsul considerably reduced fan energy consumption and carbon dioxide emissions, and gained a number of other significant benefits as well.
The three huge ID fans (left) are controlled from the electrical room (right); the three ACS 2000 drives are on the left and the UniMix switchgear on the right.
The ABB solution comprises three ACS 2000 medium voltage drives, three ACS800 low voltage drives, and UniMix medium voltage switchgear for line supply connection and backup bypass for the variable speed drives. The ACS 2000 variable speed drives - rated at 700 kW, 6.4 kV - can be directly connected to the line supply and do not require an input isolation transformer.
Prior to the installation of the ABB solution, the average daily energy consumption of the fans with damper control was 153.6 megawatt-hours. The variable speed drives have reduced this by 9 MWh to 144 MWh, which equates to €240,000 ($320,000) a year at a tariff of €0.80 ($1) per kWh.
Lower energy consumption means lower carbon dioxide emissions. The drive solution has reduced the plant’s CO2
emissions by about 4.5 tons a day – a significant reduction to the plant’s carbon footprint.
The ABB variable speed drives have also improved process control. The air flow can be controlled more accurately, faster and reliably than with dampers. Other benefits of the drive solution include lower investment and maintenance costs, reduced footprint in the electrical room, and smooth integration with existing plant infrastructure.
to learn more about the ABB drive solution for Valorsul.
The Valorsul waste-to-energy plant, Portugal.