Paper details
Most of Quebec is linked to the overall power grid, with most of the electric power supplied from large
hydroelectric dams. This is what makes Quebec’s relatively low environmental footprint possible.
There are, however, several places in Quebec that, because they are too remote, temporary installations,
or separated by a large physical barrier, cannot be connected to this shared power grid. This is the case
of the Îles-de-la-Madeleine, many first nation communities and remote, northern, mining operations.
Diesel-fueled, industrial electrical generators are used instead to supply electric power. As a
comparison point, consider a single, 100 kW generator such as the Generac SD100 generator:
Quebec, as a Canadian province, is part of the Paris accord and is bound to reduce its environmental
footprint. The Canadian government also has expressed the goal to attain net-zero emission status by
2050.1
The goal of this project is to go through some of the initial, conceptual design phase of a heat
recovery system that will reduce the environmental footprint of such a generator system. The heat
recovery system will consist of an Organic Rankine Cycle (ORC) that takes the heat from the exhaust
gas of the diesel generator to produce extra electricity
Tasks:
1. From the specification sheet of the diesel generator, identify
(a) the rate at which exhaust gases are produced by the diesel generators;(b) the exhaust temperature of the diesel generator;
(c) the amount of thermal energy in the exhaust gases if the ultimate low temperature coolant of
your ORC system is atmospheric air at 20oC;
(d) the absolute, maximum extra amount of electrical power that could be produced by the
thermal energy in the exhaust products;
(e) the rate at which diesel fuel is burned when the unit produces 100 kW (a.k.a. 100% load).
2. Draw a block diagram of the different components of the system. Identify the diesel generator
as a whole, the streams through which heat is lost (exhaust gases is one of them, there is at least
one more), and the components of a basic ORC.
3. Search for a credible source of information to identify three (3) possible working fluids that
could be used in your ORC cycle. Why did you pick those 3 fluids? Some hints:
(a) Since you are looking to use this fluid inside a Rankine cycle based device, you probably
want the critical temperature of the fluid to be above or not far below the exhaust gas
temperature.
(b) Don’t search on www.google.com, search on scholar.google.com! Google Scholar will
return only peer-reviewed, scientific journals, and patents. If you log into the university
library, you can get access to many of the papers that will be returned. Google Scholar is for
technical searches. Google is where you search for the correct order to watch Marvel
movies, or to find out Jungkook’s birthday.
(c) Don’t worry too much about being able to find thermodynamic tables for the fluids you
select, or about selecting the perfect working fluids2
. You are selecting 3 and will make
comparisons in the next task.
4. Design your ORC cycle. Select the boiler and condenser working pressures and calculate the
expected thermal efficiency and power output for your three fluids.
(a) Why did you pick those values of pressure?
(b) What is the required mass flow rate of working fluid for each case?
(c) Which fluid would you pick?
5. One way to measure pollution is to count the amount of CO2 produced, per year. For this task,
you can assume that diesel fuel is composed of molecules of C12H18 and that all carbon is
burned to produce CO2.
(a) In one year of continuous operation at 100 kW output, how many tons of CO2 are produced?
(b) If you recuperate energy from the exhaust gases to produce more electricity, how many tons
of CO2 would be avoided?
