Chef boyardee
Project undertaken in course year 2018-2019 with Precourt Institute for Energy
Project Goal
Develop a heating system that uses water-based thermal energy storage to decouple energy generation and consumption, effectively storing energy when it is cheap and dispatching when it is more expensive
Project Motivation
Electrification of residential heating systems could play a major role in diminishing the greenhouse emissions across the world.
The Central Energy Facility at Stanford (CEF) uses this same concept at university-scale. Could it be done at residential scale?
A Central Home Energy Facility (CHEF) could reduce these emissions and lower energy costs
Background
Increasing concerns about climate change and a worldwide effort to reduce greenhouse gas emissions
There is currently a lack of economic incentives for people to switch from heating homes with fossil fuels to electricity, in large part due to high electricity pricing rates from utility companies across the country
High Priority Requirements
Heat air to desired temperature of homeowner
Temperature must be adjustable
System must be able to withstand earthquakes
Ethical Considerations
System could potentially increase the amount of fossil fuel based electricity used if the economics behind it do not support renewable energy generation
System could also increase economic inequality among the Los Angeles population, our target area of focus. The socioeconomically elite can afford the capital expenditure of our system and since it will eventually save them money over the long term, our system will help them get richer while doing nothing for the poor
Solution
We estimated that a 2000 sq. ft. home in the Los Angeles area would demand a heating load of 63 MJ or less for 99% of days in a calendar year. We designed a hydronic, heat-pump powered system that could provide this heat demand and selected theoretical heat exchangers, storage tank and heat pump. We then wanted to test our design, so we created a scaled system with a singular 57 heat exchanger, smaller pump, and a smaller hot water heater that functioned as both the heat source and tank.
Full scale solution
Full-size system, with electric heat pump, storage tank, heat exchangers, water pump to store hot water, and extract the heat via heat exchanges to warm the home
Scaled model
To enable testing, the design was scaled down to a smaller tank, single heat exchanger and pump. By testing at this scale, we can demonstrate full-scale performance
Test schematic
This diagram shows the schematic behind the test setup, depicting where datapoints are gathered
Experimental setup
Small scale system test setup, depicting hot water tank with heater, Arduino control syste, water pump and heat exchanger
Heat output
Test data showing heat output from the heat exchanger. Control circuitry was in place to turn off pumps and exchanger when a specific amount of heat was extracted from the exchanger in a 10 minute period. It can be seen that the pumps and exchangers were on longer at the end of the test
Heat load at full scale
Heating loads for full scale system during peak pricing hours or the Los Angeles area. Data in yellow represents heating demands that our full scale system is able to fulfill given the possible heat output we obtained in our scaled experiment. Data in red represents heating demands would need to be met by supplemental heating sources
Additional findings
System can provide heating 85% of the year
Return on investment of 5.2 years
Student team
Future Work
Analyze the mechanics and costs of adding a thermal storage tank and heat pump to an already existing hydronic heating system, especially those that use natural gas to heat the water
Analyze the possibility of heating the thermal storage tank directly from energy produced by rooftop solar panels
Explore different sensors that we could attach to our system that would provide indications and warnings of potential failure