Environmentally friendly heating: what’s the solution?
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Environmentally friendly heating: what’s the solution?
At McMaster University in Canada, Dr Marilyn Lightstone is a Professor of Mechanical Engineering researching how to reduce greenhouse gas emissions caused by the existing buildings and homes in Canada. Since energy use in buildings generates about 18% of the country’s emissions, this work is critical if Canada is to reach its goal of being net-zero by 2050. Could ground source heat pumps be the solution?
Talk like a mechanical engineer
Borehole — a long narrow hole drilled into the ground
Carbon dioxide (CO2) — a greenhouse gas that affects the climate and environment
Electrical grid — the network that supplies electricity from generators to consumers
Existing building stock — the buildings that already exist in a place
Greenhouse gases — gases in the atmosphere that raise the temperature of the Earth
Hybrid heating — using a combination of heating systems
Net-zero — achieving a balance where no more greenhouse gases are added into the atmosphere
Space heating — heating of spaces for human comfort
Temporal variability — variables (changes or differences) that occur over a period of time
Almost a fifth of Canada’s greenhouse gas emissions are caused by energy use in buildings, including heating, lighting and running appliances such as kettles and refrigerators. “Due to the cold Canadian climate, space heating is responsible for nearly 62% of residential energy use,” says Dr Marilyn Lightstone, Professor of Mechanical Engineering at McMaster University who is working on reducing the emissions of existing buildings in Canada. As heating uses more energy than anything else in Canadian homes, making heating systems as efficient as possible is incredibly important for trying to reduce the impact of the climate crisis. “Canada has committed to reduce greenhouse gas emissions by 2030 to 40 to 45% below the levels they were in 2005. It also has a further goal of net-zero emissions by 2050,” says Marilyn. “There is a short time window to take action to mitigate the most devastating impacts of climate change.”
What is Marilyn working on?
While new buildings must meet special energy regulations, older buildings often have poor insulation and single pane windows (which allow more heat to escape), making it harder to reduce their environmental impact. To reduce the carbon dioxide output caused by heating these buildings, Marilyn is researching efficient household heating systems, such as heat pumps.
Currently, there are air source, water source and ground source heat pumps, all of which work by using electricity to transfer energy from a cold space to a warm space. Note that thermal energy will naturally flow from hot to cold, so electrical work is required to transfer heat in the opposite direction.
Ground source heat pumps work by taking advantage of the heat stored just below the surface of the Earth. “A ground source heat pump accesses the vast amount of thermal energy existing in the ground and transfers that energy through a refrigeration cycle to the building interior,” explains Marilyn.
These heat pumps are extremely efficient. “The thermal energy transferred to the house is close to four times the electrical energy used by the heat pump compressor,” says Marilyn. As the ground temperature is unaffected by air temperature and stays about the same all year round, these heat pumps still work well during cold weather – which is perfect for Canada’s winters, when daily average temperatures can be well below 0 °C.
However, installing a ground source heat pump is a huge and expensive undertaking, as it requires drilling deep boreholes into the ground. The boreholes contain heat exchangers which allow for heat transfer from the ground to a working fluid. A heat pump is then used to transfer the energy from the working fluid to the interior of a building. “If a ground source heat pump is using vertical boreholes, they need to go down to depths of 100 metres or more – longer than a football field,” says Marilyn.
Reference
https://doi.org/10.33424/FUTURUM605
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Due to the high installation costs of a ground source heat pump, many homeowners will install air source heat pumps instead. Air source heat pumps transfer energy from the outdoor air to the interior of the building. The challenge with air source heat pumps is that their performance drops as the outdoor temperature declines. That means that when the outdoor temperature is very cold (below -10 °C), a lot of electricity is required to run the heat pump.
Are heat pumps the only answer?
Marilyn’s research is now focusing on the benefits of a smart hybrid heating system, where existing high efficiency gas furnaces that are already installed in buildings are used in combination with new heat pumps. While heat pumps are usually the most environmentally friendly option, there are times when using a high efficiency natural gas furnace is the better choice.
To understand this, think about how at certain times of the day everyone wants to use electricity at the same time. The morning shower rush, for example, or the point in the evening when most people start to cook dinner. “A key challenge faced by electricity generators is the large temporal variability in electricity demand – that is, how electricity use varies throughout the day and throughout the working week and weekend. Since electricity is hard to store, electricity generation must equal the demand at any particular time,” explains Marilyn. When one of these high-usage moments hits, the increased demand for electricity is usually met by turning on natural gas power plants. “These plants release greenhouse gases as a product of the combustion process,” explains Marilyn. As a result, during these times, using electricity (and therefore, heat pumps) produces a large amount of carbon dioxide.
A combined solution
This is when the smart hybrid heating system that Marilyn is researching would work well. These systems would have a smart controller that ‘decides’ whether to use a building’s heat pump or gas furnace at different times of the day, depending on which would produce the least emissions. “For example, during very cold weather when air source heat pump performance degrades, the heat pump would be turned off, and the natural gas furnace would be used for building heating,” says Marilyn.
There is still lots of work that mechanical engineers like Marilyn need to do before this work is put into practice – such as educating members of the public and heating, ventilation and air conditioning installers. But keep an eye out for how homes and buildings are heated over the next few years – you just might start to see some changes!
Dr Marilyn Lightstone
Department of Mechanical Engineering, McMaster University, Canada
Fields of research: Mechanical engineering, computational fluid dynamics, heat transfer, turbulent flows
Research project: Investigating the role of heat pumps in reducing greenhouse gas emissions
DOI: 10.33424/FUTURUM605
About mechanical engineering
Choosing to work in mechanical engineering leads to a wide range of careers and pathways. You might end up working in the renewable energy sector installing wind turbines, the oil and gas industry decommissioning rigs, or the space sector building telescopes! Jobs can range from writing code for software to designing and making new pieces of machinery.
“Mechanical engineering is a broad discipline that includes manufacturing, robotics, energy systems, biomedical engineering and many other topics,” says Marilyn. “If you enjoy maths and physics, love brainstorming and problem solving, and are interested in how things are made and how they work, then mechanical engineering might be the path for you.”
Working in this field is incredibly rewarding and brings benefits to people all over the world. “With our ageing population, there will be a need for new biomedical devices and systems to help with age-related issues and to enhance people’s quality of life,” explains Marilyn. Developments in robotics and artificial intelligence are opening up hundreds of new possibilities in this field, making it an exciting time to start a career in mechanical engineering.
Mechanical engineers have a huge role to play in helping mitigate the impacts of the climate crisis too, as they can design new machinery and systems that reduce emissions and manage waste. “Climate change has also created a resurgence in nuclear energy as a reliable low carbon electricity generation method, so opportunities in this area are also likely for the next generation of mechanical engineers,” says Marilyn.
Pathway from school to mechanical engineering
During high school, build a strong foundation in mathematics, chemistry and physics.
“The Faculty of Engineering at McMaster University offers numerous outreach events including clubs and summer camps for children and young people spanning grades three through 12. These events aim to encourage participants to explore science, technology, engineering and mathematics in a fun and inclusive way,” says Marilyn.
Marilyn recommends visiting local universities during their open days and talking to staff and students about mechanical engineering. “University websites also have information about their engineering programmes and related career opportunities,” she says.
The New Engineer outlines some of the Canadian universities that offer mechanical engineering degrees.
You will also need to complete a master’s degree and PhD. if you want to work as a professor like Marilyn.
Explore careers in mechanical engineering
Indeed Canada has some great information on getting into mechanical engineering and how to become qualified.
The Institution of Mechanical Engineers provides a wealth of information about careers in engineering.
Learn about the range of mechanical engineering breakthroughs over the years to see where the field might take you.
Meet Marilyn
When I was a child, my brothers and I used magnifying glasses in the sun to burn through leaves – in those days our parents let us run wild, so health and safety was less of a worry back then! I remember being amazed by the power of the sun, and I asked my father why we don’t use the sun to heat our homes. He replied that there wasn’t a great way to store the sun’s energy in the summer for use in the winter. That sparked my interest in solar thermal energy and thermal energy storage. Fortunately, I also had an aptitude for mathematics and physics which made engineering a logical career choice.
I have been lucky to have had outstanding mentors throughout my student years and during my career. These mentors have had a profound impact on my career and in my approach to tackling scientific problems. Before becoming a professor, I worked in the nuclear industry for a few years, focusing on nuclear safety analysis. Bringing that experience into my teaching and research has helped me to be a better professor.
As a Professor of Mechanical Engineering, my day involves teaching both undergraduate and graduate courses in fluid mechanics. I also have graduate students who are working on master’s or PhD. degrees, and my time is spent on supervising their research. Working with graduate students on research and seeing them flourish in their learning and subsequent careers is truly rewarding. It has been a great privilege to work with young people and to help them develop the skills they will need for successful careers.
From 2013 to 2023, I had the privilege of being Chair of the Department of Mechanical Engineering at McMaster University and spent the bulk of my time on the administration of the department. This role provided some of my proudest career achievements. During those ten years, I oversaw a substantial revitalisation of the department, hired many new faculty members and supported the successful shift to online learning during the pandemic.
Marilyn’s top tips
1. Think about what your passion is and what makes you excited. Try and find people who work in that area and learn as much as you can from them.
2. Work hard to get the skills you need.
3. Keep having fun; make time for your family and the things you find enjoyable.
Do you have a question for Marilyn?
Write it in the comments box below and Marilyn will get back to you. (Remember, researchers are very busy people, so you may have to wait a few days.)
Read about how biomechanical engineers are helping to detect and prevent brain injuries:
futurumcareers.com/how-can-we-detect-and-prevent-brain-injuries
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