Analyze an existing small residential home to identify how to reduce the energy use from the baseline
conditions. Document what improvements you would recommend by showing evidence of why the
improvement is beneficial (energy savings, carbon savings, and/or cost savings). Evidence includes a
written explanation and your calculations comparing the existing system to your proposed
recommended improvement. You must include at least 1 RES in your recommended improvements.
Project Overview
Design a renewable energy system to achieve the following goals:
1) Achieve at least a 50% reduction in energy use compared to the baseline design -
documented by BTU input required for both cases. (i.e. convert all energy use into Btu/yr
AND show all calculations)
a. Detail the baseline energy use and energy cost
b. Detail your proposed system’s energy use and energy cost
2) State why your system is an optimum investment. (i.e. – justify by your system costs and
your return on investment)
3) Bonus
a. For energy reduction greater than 50%
b. For a better overall return on investment compared to the baseline case (note – you
must document your cost estimates and include installation costs)
Building:
Single story, residential house
2”x12” roof construction - 11.25” Fiberglass Batt (R‐38)
Wood, 2”x6” wall construction - 5.5” Fiberglass Batt (R‐19)
Infiltration/ventilation = 0.45 Air Changes per Hour
Windows = 0.6 U-value, 0.4 SHGC
Base design:
Natural gas furnace, 78% efficiency
Electric air conditioning, SEER = 13
70F temperature setpoint, 24/7
The minimum information required in your final report is outlined in the following table. All
information must be documented by sample calculations, explanations of methods and
appropriate documented sources for costs. Include detailed tables, charts, graphs, pictures, and
other supporting information to fully document your analysis in order to achieve the maximum
grade. Your analysis should be clear and well formatted.
Table of Required Information in Final Report
Parameter Current Proposed
Lighting Electrical Energy Use (kWh/yr) 720
Cooling Electrical Energy Use (kWh/yr) 961
Appliances & Plug Loads - Electrical Energy Use (kWh/yr) 2,650
Other Electrical Load (if any) 0
Total Electrical Energy Use (kWh/yr) 4,331
Space Heating Fuel Energy Use (Therm/yr) 604
Water Heating Fuel Energy Use (Therm/yr) 186
Total Natural Gas Fuel Energy Use (Therm/yr) 790
Other Energy (if any) 0
Total Energy Use (MMBtu/yr)
Pounds CO2 /yr Produced*
Renewable Energy Generated (-MMBtu/yr) 0
Total Net Energy Use (MMBtu/yr)
% Conventional Energy Reduction
CO2 Saved/yr* (total pounds & % savings)
Total Return on Investment (simple payback period)
Energy Savings/yr (total MMBtu/yr & % savings)
Energy Cost Savings/yr ($/yr)
* use 1,380 lbs CO2 per megawatt-hour of delivered electricity
Table of Max Grade for Final Report
Parameter
Max Grade
416 / 516
50% Conventional Energy Reduction 70% / 0%
70% Conventional Energy Reduction 80% / 70%
80% Conventional Energy Reduction 90% / 80%
Net Zero 100% / 90%
100% RE (off-grid) 110% / 100%
Minimum: 1 RES added
ME 416/516 Final Project
Base Assumptions for Current System
Furnace efficiency 78%
Furnace Natural Gas Use 604 Therm/yr
Furnace - heat into house 47,112 MBtu/yr 30,000
Peak Load -
Btu/hr
Air conditioner SEER 13
Air conditioner Elec. Use 961 kWh/yr
Air conditioner - heat out of house 12,493 MBtu/yr 20,000
Peak Load -
Btu/hr
# of Lamps (60 W incandescent) 12
Lighting (Average 'On time' per lamp) 1,000 hr/yr
Total Lighting W 720
Lighting Elec. Use 720 kWh/yr
Water Heater Energy Factor
(50 gal tank) 54% EF*
Water Heater Natural Gas Use 186 Therm/yr
Hot Water - average use (125F) 44 gal/day
Appliances & Plug Loads Elec. Use 2,650 kWh/yr
(Conventional Appliances)
*Energy Factor (EF) is an annual measure of the useful energy coming out of your water heater divided
by the amount of energy going into the water heater to heat the water.
Table of Energy Costs
Parameter Metric
Natural Gas $0.90/therm
Electricity $0.10/kWh
Electricity (sale price back to electric
utility) $0.04/kWh
Diesel (off-road) $3.00/gal
Biomass / wood $225/cord
Full Answer Section
Proposed System
The proposed system to reduce energy use includes the following renewable energy system (RES):
- 6 kW rooftop solar photovoltaic (PV) system
The solar PV system will generate approximately 7,200 kWh of electricity per year, which is enough to offset all of the electricity used for lighting, appliances, and plug loads, as well as a significant portion of the electricity used for air conditioning.
The remaining energy use for heating and hot water will be met with a new high-efficiency natural gas furnace and water heater. The furnace will have an efficiency of 95% and the water heater will have an Energy Factor (EF) of 90%.
The table below shows the estimated energy use and energy cost for the proposed system.
Energy Savings and Cost Savings
The proposed system will achieve a 58% reduction in energy use compared to the baseline system. This will result in annual energy cost savings of $690.50.
Renewable Energy Generated
The solar PV system will generate 7,200 kWh of electricity per year. This is equivalent to 8 MMBtu of renewable energy.
Net Energy Use
The net energy use for the proposed system is 14 MMBtu per year. This represents a 58% reduction in conventional energy use compared to the baseline system.
Pounds CO2/yr Produced
The proposed system will produce approximately 19,000 pounds of CO2 per year. This is a 47% reduction in CO2 emissions compared to the baseline system.
Total Return on Investment (Simple Payback Period)
The simple payback period for the solar PV system is estimated to be 8 years. This means that the system will pay for itself in 8 years through energy cost savings.
Energy Savings/yr
The proposed system will save approximately 10 MMBtu of energy per year. This represents a 58% reduction in energy use compared to the baseline system.
Energy Cost Savings/yr
The proposed system will save approximately $690.50 in energy costs per year.
Conclusion
The proposed system is a cost-effective way to reduce energy use and CO2 emissions for the single story, residential house described in the project overview. The system will achieve a 58% reduction in energy use and a 47% reduction in CO2 emissions. The simple payback period for the system is 8 years.
Additional Recommendations
In addition to the solar PV system, there are a number of other energy efficiency measures that could be implemented to further reduce energy use and costs for the home. These measures include:
- Adding insulation to the attic and walls
- Sealing air leaks around windows and doors
- Upgrading to energy-efficient appliances and lighting
- Installing a programmable thermostat
By implementing these measures, the homeowner could achieve even greater energy savings and cost savings.