Politics of pollution: current event – largest coal plant in the US likely to close
March 12th Lab
Colby’s sustainability coordinator will provide an introduction to her work here and help frame your final projects in terms of relevant information we might provide and questions to be answered about the energy systems in SSW.
Watch this video on creating a loan financing template in Excel
In-lab assignment
Other Resources: A very good article on PV-Battery Systems – AKA Solar Power Isalnds.
March 9, 2018
Maine Huts & Trails overnight
Meet behind the Keyes building at 1pm with your gear
March 8, 2018
Energy Systems Used at Maine Huts & Trails
[Homework Assignment due 15-Mar-18 @ 8am]
Composting Toilets:
The composting toilet system at Flagstaff Hut was manufactured by Clivus New England. The manufacturer’s web site has a good link to the the technology. Key components of the system include toilets that flush with a 3 oz water/foam mixture, waterless urinals, and a central composting camber in the basement of the hut. The compost pile is kept warm, oxygenated, and moist to facilitate aerobic oxidation of human dejecta. Human waste is mostly water (Composition of Human Dejecta) and organic carbon so the oxidation of waste produces carbon dioxide and water vapor that leave the compost chamber as gas. The residual solids are mostly inorganic phosphorus, calcium, and potassium salts that represent less than 10% of the initial waste volume. 1) An interesting calculation would be the expected annual mass of composted material produced by 500 hut visitors per month.
Interesting technical challenges are the physical limitations of component placement since gravity and very low water volumes are used to carry waste from the bathrooms to the compost facility. The Clivus system does require regular maintenance and, therefore, requires easy access.
Urine is high in nitrogen and the composting process converts most of the nitrogen, urea, to soluble nitrate or nitrite that collects in the liquid sump in the bottom of the composter. This liquid is pumped out of the system and added to the gray water of the hut. It would be interesting to know more about the gray water system and regulations on gray water system placement in Maine. Would it “pay” to install this system in your own home? What is the market for Clivus systems. The hut crew sold the benefits of the system based on water savings? Is this the real environmental and economic cost?
Heating System
The heating system was manufactured by Tarm Biomass. The HS Tarm Solo Innova 50 boiler is about 80% efficient, has a normal output of 171,000 BTU/hr, and the hut burns about 20 cords of dry wood per year to heat the buildings and produce hot water. The plumbing schematics from Tarm are pretty close to the installed system.
2) Interesting calculations would be the total energy produced by 20 cords of wood in BTUs and joules and equivalent amount of oil or natural gas required to produce this amount of heat. The Flagstaff Hut installation uses an 850 gallon water tank to store heat from the Tarm boiler. Assuming the water used for storage has a temperature swing of 100 oF (80–> 180), what is the total heat stored in the tank and how long would it take the boiler to produce this much heat. Why was my shower cold on Saturday morning? The hut uses a backup propane heater which they use in the summer. Why is the backup heater important? Would it “pay” to install this system in your own home?
Electrical System
Pika Energy Systems – the future?
The hut runs on standard 120/220 volt electrical service. The hut is not connected to electrical grid and must generate all of the electrical power using solar panels and a propane generator. The solar panels produce 5.6 kW of DC electrical power at peak performance and store this energy in twenty four, two volt, lead/acid batteries. The total capacity of the batteries is 24 kW-hr. As a good assumption, a solar system rated at 1 kW of power at full sum will produce 1000 kW-hr of total electrical energy in one year (stay tuned for this calculation).
The solar panels can not meet the entire electrical demand of the hut so a propane generator is used to supply additional power. The generator uses about 400 gallons of propane a year. Key to operation of the system is the Outback inverter/control system that can charge the batteries from AC or DC power inputs and deliver power to the hut from AC (generator) or DC outputs (battery).
A few basics on propane generators:
- It requires 2 horsepower to produce 1000 watts of energy per hour under load.
- Under load, each horsepower consumes 10,000 BTU per hour.
- Propane contains 92,000 BTU per gallon.
- Propane weighs 4.2 pounds per gallon.
The hut crew mentioned that the generator always came on when the guests were using a lot of water and suspected that the water pump was using a lot of power. Pumping water requires very little energy (work = mgh) once the pump is started. However, the starting load on the electrical system to start the pump is very large. One solution may be to install a smaller water pump. It would pump longer, but require a reduced starting load. If the Outback control system logs power usage it would be informative to look at the electrical load profile of the hut to determine if additional energy efficiency is possible.
3) Interesting calculations would be the total electrical energy produced by the solar and generator systems over the entire year. How does the fuel-only cost of these systems compare to residential electrical costs of 0.13 $/kWh? If an installed propane generator costs $5000 and the hut’s solar system costs $25,000 what is the simple 25 year cost of running both systems?
Further Reading:
Off-Grid Feasibility and Sustainable Load Shifting
Rolls Battery, Look at a Spec Sheet
Maine Public Radio Story on Off-Grid homes – start at 6 minutes
March 6, 2018
Final Project: Building Energy Systems Review for SSW
Due date: May 10th, 2018 @ 8am
Teams:
- Heating & Cooling systems
- Electrical systems
- Comfort survey
Some questions to think about:
1. How does actual building energy performance compare to what was expected at time of LEED certification?
2. Benchmark the building energy performance per LEED requirements. Does it meet the minimum energy performance threshold?
3. Identify at least three (?) energy conservation measures. Calculate savings, costs, simple payback. Consider lighting, lighting controls, HVAC/controls, any issues identified by occupant comfort survey.
4. Is the geothermal system performing as expected?
5. Is it possible to calculate energy by end use? Hating, cooling, lighting, plug loads?
6. Conduct thermal comfort survey
7. Compare SSW LEED certification to current LEED version 4 requirements. Would SSW meet the new requirements?
8. Calculate carbon emissions savings from geothermal systems and the PV array. What are the associated financial costs and savings? Does this approach make sense for future campus buildings? If so, under what conditions?
March 5th Lab
Meet in the lobby of the Shair-Swenson-Watson building (next to the Davis building) at 1pm for a tour of the energy systems in this building
Miscellaneous tidbits of information:
- Colby’s renewable energy credits (RECs) would be worth $250/MWh if the energy were produced in Massachusetts. Here in Maine, ours are worth around $24-$28 per MWh. We would expect a total of $55,000-$65,000 per year if we sold our solar RECs in the Massachusetts market (2,300 MWh). In contrast, we recently paid $0.49/MWh for 15,300 MWh worth of RECs (~$7500 for RECs to offset all campus purchased electricity).
- Shair-Swenson-Watson (SSW) Solar Production (Excel worksheet)
- Thermal comfort Survey developed for the Grossman Renovation and designed to meet the requirements of the LEED credit.
- SSW energy systems snapshot
- Recent energy use data from SSW (Excel worksheet)
- Do we have sewer/water and trash/recycling data by building? If not, we may be able to get plumbing fixture counts and flow rates off the building construction drawings and we can do some calculations.
- Climate Data for thermal and solar analysis: Colby Quad_48, Colby Quad_47, Colby Quad_46, Colby Quad_45, Colby Quad_44, Colby Quad_43, Colby Quad_42
February 20th, 2018
Review of Economics – part 2
Lecture notes
Handout
A macro view of the economy
February 19th Lab
February 15th, 2018
Review of Economics
Lecture Notes
Handout
REC Arbitrage
February 13th, 2018
Combustion
Lecture Notes
Test Your Understanding – How much energy is required for a 10 minute shower at Colby?