Economics of Passive Solar and Zero Energy Homes Jeff Tiller, PE ASU Energy Center / Department of Technology Southface North Carolina tillerjs@appstate.edu 828-262-6355
Projected Residential Energy Use NC Residential Energy Use (BBtu) 450,000 400,000 350,000 300,000 250,000 200,000 150,000 100,000 50,000 0 What can we do about this? Solar Wood Coal LPG Kerosene NaturalGas Electricity 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 Global Insight Report on Energy Use in North Carolina, 2003
Final Preliminary Scenario NC Residential Energy Use (BBtu) 450,000 400,000 350,000 300,000 250,000 200,000 150,000 100,000 New Home Savings Existing Home Savings Energy Efficient Scenario 50,000 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020
Towards Zero Energy Step 1: High Efficiency Insulation systems; high efficiency windows Air sealing Duct sealing HVAC efficiency Appliances and lighting Energy Star Systems Vision / Environments for Living NC HealthyBuilt Homes Indoor air quality / ventilation/ moisture control Step 2: Passive Solar Design/ Natural Cooling Features Step 3: Solar Thermal Step 4: Green Building Features Step 4: Renewable Electricity
Livermore, CA 3,070-square-foot house A 3.6-kW PV array Solar hot water Night breeze comfort system Low-E windows Fly ash concrete
Tucson, AZ 1,718 square feet 1kW PV system Solar hot water Low-e windows All homes in urban subdivision exceed model energy code by 50%
Califon, NJ Year 1900 farmhouse 1,400 square feet 7.2 kw PV system Blown-in cellulose Insulated siding
Fargo, GA 1,836 square feet Nonvented conditioned crawl space 4 kw PV array Structural insulated panels Recycled content decking Compact fluorescent lights High performance HVAC Low E windows
New Smyrna, FL A duplex with 1,736 sq ft of living area for unit 1 and 1,224 sq ft of living area for unit 2. 28 amorphous silicon modules bonded to the metal roof panels Light-colored exterior walls Large overhangs and porches help to shade the double-glazed, highperformance windows
Lakeland, FL 1998 side-by-side comparison Twelve modules facing south: 2,700 W Six modules face west: 1,350 W The combined capacity: 4,050 W Annual energy use Base home = 22,500 kwh/yr PVRES = 1,500 kwh/yr Design features saved 70% compared to base case PV system saved 22%
Systems Vision Project of Advanced Energy High performance affordable homes Three inspections required: framing, insulation, final Ventilation and combustion safety Efficiency standard Energy Star minimum
Passive Solar Design Most affordable designs Single story Limited window area Simple appearance; low roof pitch No attention to orientation Passive solar design effort Reorient rooms and windows Insulated slab floor Insulation, air sealing, duct sealing details High efficiency HVAC
Typical Design BATH LAUNDRY DINING TV BEDROOM SD UTILITY BATH KITCHEN CLOSET CLOSET CLOSET CLOSET HALL SD 1,147 sq ft SD CLOSET TV SD BEDROOM BEDROOM CLOSET LIVING AREA TV 1063 sq ft
Passive Solar Option TV BEDROOM CLOSET CLOSET CLOSET SD LAUNDRY BATH UTILITY CLOSET BATH KITCHEN HALL SD SD CLOSET DINING TV Same window area 90 sq ft face south (8%) Savings: % heating % cooling SD BEDROOM BEDROOM CLOSET LIVING AREA TV 1063 sq ft
Passive vs. Non-Passive Plan
Available on-line at www.ncenergystar.org
Affordable Passive Solar Plans
Affordable Passive Solar Plans
Enthusiastic Response Habitat for Humanity Chapters Redesigned homes for Avery, Catawba Valley, and Watauga Also working with Asheville, North Charlotte, Caldwell County and Alexander County Housing Authorities/ Other Groups NW Housing Authority Watauga Youth Build Mountain Housing
NW Housing Authority Currently meeting Systems Vision program guidelines Agreed to adopt new designs Agreed to meet NC HealthyBuilt Home criteria First project: 18-home subdivision in Jefferson, NC The Oaks
Baby Cape Design
Zero Energy Plan design Catawba Valley Habitat for Humanity Project in Hickory, NC
The Zero Energy Home
Insulated Foundation
Framing
Framing Details
Framing Details
Icynene Insulation
Truss Design
HVAC System Total cooling load less than 1 ton Geothermal HVAC Typical cfm to bedrooms less than 75 cfm Most of ductwork in conditioned space
Passive Solar Design
Energy Efficient Appliances and Fixtures
Appliances and Lighting Thor washer-dryer combination No dryer vent, runs on 110 V, liquid water drain Energy Star tm refrigerator and dishwasher Compact fluorescent lighting Low sone, effective Panasonic exhaust fans Enthalpy Recovery Ventilation system Insulated window blinds
Problems Along the Way South window design Corner structure Quest for high SHGC; Window delivery Truss delivery HVAC loads Solar water heating Cost Installation Photovoltaics UL-listing Interconnection Meter Fee The Freezer
Wall Framing Issue
Truss Issue
Solar Energy Systems
The Finished House
The power bills 4.5 kw Aug Sep kwh used 532 467 kwh produced 423 663 Net energy -109 196 Cumulative net energy -109 87
The power generation bills
NC GreenPower Payment
Solar Water Heating Installed: $4,500 (maxes out tax credit) Decided to hire installer (or self install) Three bids (Two collectors, 80-gallon storage with built-in heat exchanger, pumps, all key parts) $2,900 $2,500 $2,200
Solar Hot Water Economics System materials $2,500 Installation 1,500 Total $4,000 Federal tax credit (30%) 1,200 Subtotal $2,800 NC tax credit (35%) 980 Net total $1,820 Annual savings 300 Payback period (years) 6 Mortgage pmts (20 yr, 7%) $170/ yr
Photovoltaic Economics Economic Analysis System cost 25,000 Federal tax credit 0.3 3,000 Net cost 22,000 State tax credit 0.35 3,000 Net cost 19,000 Base credit rate 0.240 Downpayment 0.15 3,750 Points 0.015 375 Total Financing Cost 4,125 Mortgage Principal 21,250 Interest 0.07 Term 30 Annual Mortgage Payments 1,697
PV Economics Income Hours per day 4.5 kwh per day 20.25 kwh per year 7,391 Average avoided cost rate 0.0375 277 NC GreenPower rate 0.18 1,330 Total income 1,608
PV Renewable Electricity System 4.5 kw array designed to balance home s electricity demand Connected to grid via Duke Power Generator on NC GreenPower Program
Energy Stars of All Sizes