Project no. 307
Combined Cooling, Heating and Power: Using Waste
Gasification for a Tri-Generation Plant in a Hospital
V. Amato, A. Buffet, B. L. Oyarzabal, L. Pardini, A. Pasquali
Technical University of Denmark, Department of Mechanical Engineering
Waste management is among the most pressing issues in environmental protection. The EU
28-member states produce around 242 million tons of waste every year, of which nearly 210
million come from the EU 15; Spain, France and Italy are the top three countries that
dispose waste in landfill sites. Therefore, there is still a huge improvement to be done by
some Mediterranean countries of the EU. Electricity production is also a big concern these
days. This production is becoming more environmentally friendly in some European
countries. In Denmark 44% of the electricity production came from wind energy in 2017.
Nevertheless, this is not a truthful picture of the current situation in the world. In 2014,
22,430 TWh were produced and less than 24% came from renewable energies. Indeed,
39% was produced using coal and 22% with gas. The rest was shared between nuclear, oil
and other kind of sources. Hence, electricity production pollutes and enhances global
warming since coal and gas are the most used resources.
Waste-to-energy recovery technologies are a clever solution to these main problems. One of
the possible technologies is gasification, which produces a syngas from the waste that can
be cleaned afterwards so that it does not pollute when released in the atmosphere. One
could think of a small environment where a significant amount of waste is produced and
energy is required and hospitals are such. Hospitals could be described as small villages as
many people work, eat and are healed. Consequently, hospitals have three different
demands at the same time: heating, cooling and electricity. A plant that consists of a
gasificator that turns such waste into clean fuel, 4 micro-turbines and an absorption chiller
has been designed.
The fuel used is its own waste and municipal waste from the neighborhoods of the hospital.
The turbines generate an electric power of 174.31kW and the absorption chiller provides
369.26kW of cooling and 971.42kW of heating. Two optimizations have been carried out on
the moisture content of the waste after the dryer and on the exhaust gases temperature. It
turned out that a higher moisture decreases significantly the power output and that the
optimal temperature for the gasses is 80°C. It has been found that the Net Present Value of
the plant is 2,804,131€, which makes the plant worth building not only for ecological
reasons, but also from an economic perspective.
Regarding the input necessity, it is clear that the generation of refuse from the hospital does
not cover the waste input requirement and waste from other sources will be needed. Plant
design-wise, the less moisture of the waste and the lowest possible temperature of the
exhaust gasses are preferable. The NPV of the plant is positive and the payback time is
found to be 7.3 years. As a consequence, based on the assumption made in this study, the
plant is worth building as a significant amount of money will be saved. This certain
conclusion could be considered very favorable in a perspective of transition to sustainable