District Energy Systems
Are district energy systems centralized or decentralized?
Centralized
Is geo-exchange a renewable energy source or a storage system?
Geo-exchange uses conductivity with the earth to transfer heat to and from the constant earth temperature of 50 - 55 degrees, using the earth as a storage system.
Is solar PV a renewable energy source?
Yes-- unlike geo-exchange, solar photovoltaics generate electricity, which can be used onsite or offsite, without operational carbon emissions. Other renewable resources include wind and hydro power. Nuclear is not renewable, but does not emit operational carbon.
What are the top 3 building materials that emit embodied carbon in their lifetime?
1. Concrete. 2. Steel. 3 Aluminum.
Concrete emits > 11% of global carbon emissions, steel 10%, aluminum 1.5%
Is embodied carbon tracked in Scope 1, 2 or 3?
Scope 3 -- although many of our clients are not yet tracking this.
What efficiencies do district systems offer?
The scale allows for high-performance equipment, renewables, geo-exchange, energy and water use reductions, staffing efficiencies.
What is the difference between geothermal and geo-exchange?
'Geothermal' taps into extremely hot underground water sources, like the 'Old Faithful' geyser in Yellowstone. Geowells that use geo-exchange are conducting moderate typical ground temperatures of 50-55 with a water loop, closed or open systems
What is the difference between solar photovoltaics and solar thermal?
Solar PV generates electricity, which can be used for heating, cooling, lighting, or hot water heating. Solar thermal heats water, which can be used for domestic hot water use, swimming pools, and radiant heating, with backup systems.
If concrete were a country, how would it rank among carbon emitters?
3rd after China and the USA, and more than India.
What equipment forms the backbone of a decarbonized central plant?
Heat recovery, especially Heat Recovery Chillers. They capture waste heat and use less water for cooling towers.
Why are mixed-use programs great for district energy?
Different users use energy at different times of day/week/year, allowing for the 'harvesting' of simultaneous heating and cooling
What are ideal locations for geowells?
Athletics and recreation fields, open space parks, plazas or quads, parking lots. Not prospective building sites for buildings, garages, specimen trees, underground utility corridors
What are ideal locations for solar PV?
Rooftops, trellises over parking lots and walks, ground-mounted, southern facades.
Best rooftops are: large, flat, newly-roofed.
What is the unit of measurement for embodied carbon?
For buildings= MTCO2e/m2 = Metric tons of carbon dioxide per meter square of construction.
For materials, GWP (Global Warming Potential) is in kgCO2e per kg, m2 or m3, depending on the material, and is reported in EPDs, Environmental Product Declarations.
What are the considerations for building offsite renewable energy?
Community or municipal aggregator programs, additionality, cap and trade programs such as RECs (Renewable Energy Credits)
Why are campuses great examples of district energy systems?
Single owner, single operator, mixed use communities
How deep are geowells?
Typically 500-850-1000-1500', depending on soil conditions and urban density
What angle is best for solar PV?
Depends on the latitude above/below the equator
What materials have the lowest embodied carbon?
Mass timber, wood, or other biogenic materials that store and sequester carbon. But the best is... building reuse!
How do we know if we can put solar on an existing roof?
Structural engineering evaluation if the existing structure can support an additional 5 - 7 lbs/SF on the roof, plus a new roof, plus conduit to the electrical room, plus space in the electrical room for the inverter and panel.
Globally, what country operates with 96% district energy systems, in their cities and towns?
Denmark -- but there are many other examples, including in Canada, Finland, and others. Why do you think that is? Do we have projects where this might be applicable? Why?
How do we know if the soil conditions are appropriate?
Geotechnical engineers will determine if sufficient soil information is available, or if a test well is needed (typically $30 - 50K)
C.Scale can calculate the % of solar needed to power a project. MEP Engineers can, too!
What is a reasonable design guideline for embodied carbon for construction?
300 - 500 kgCO2e / m2 - and will be lower with biogenic materials.
How are P3s (Public Private Partnerships) used for energy?
A PPA (Public Private Partnerships) builds and operates solar PV arrays on private property. EaaS (Energy as a Service) companies build and operate district energy systems.