🌊 Commercial Wastewater Heat Recovery (WHR) & Sewer Sizer

SHARC & Raw Sewage Thermal Extraction
Institutional Wastewater Heat Recovery (WHR) & Sewer Thermal Energy Extraction Sizer. Model continuous raw wastewater / greywater thermal harvesting (65°F–75°F year-round source), water-to-water heat pump COP (4.5–5.8), natural gas domestic hot water (DHW) displacement, IRA Section 48 ITC (30%–50%), and 20-year LCOH/NPV economics.
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WHR Facility Archetype:
💧 Wastewater Stream & Thermal Characteristics
GPD
Gallons per day of raw drain / sewer discharge.
°F
Typical municipal sewer: 65°F–75°F; Laundry: 85°F–105°F.
°F Drop
Temperature delta extracted before discharge (e.g. 72°F → 60°F).
Hours/day
Concentrated diurnal flow window.
⚙️ WHR Heat Exchanger & Water-to-Water Heat Pump
%
Fouling resistance derate for raw sewage exchangers.
COP
High COP driven by warm 65°F+ sewage evaporator source.
°F
Target potable DHW or space heating water loop.
💰 Tariffs, Gas Displacement & IRA ITC
$/therm
%
$/kWh
$/GPD Capacity
Screening skid, heat exchangers, W2W heat pump & DDC.
$ Lump Sum
Hourly Thermal Harvesting
315 MBH
26.3 Tons Continuous Thermal Power
Annual Boiler Gas Displaced
22,480 Therms
$28,100/yr Fuel Combustion Eliminated
Net Operating Savings
$21,450/yr
119 Metric Tons CO₂ Avoided/yr
Post-Incentive Net Capital
$169,250
Simple Payback: 7.9 Years
🌊 Wastewater Thermal Energy Exchange (Closed-Loop Hydronic Flow)
Constant 65°F–75°F Thermal Mine
📑 Engineering Spec & Environmental Yield
Design Parameter / Metric Standard Gas Boiler DHW Wastewater Heat Recovery (WHR) Variance / Net Economic Benefit
Thermal Energy Source Temperature Ambient Combustion Air (0°F - 95°F) 72°F Raw Wastewater Stream Constant High-Evaporator Temp
Thermal Efficiency / COP 82% Thermal Efficiency COP 4.80 (480% Equivalent) +398% Energy Multiplier
Annual Fossil Gas Consumption 22,480 Therms / yr 0 Therms (100% Electrified) -100% On-Site Gas Eliminated
Annual Electricity Consumption 1,850 kWh (Boiler Fans/Pumps) 51,150 kWh (W2W Heat Pump Compressor) +$6,409/yr Electric Offset
Annual Carbon Emissions (Scope 1) 119.1 Metric Tons CO₂ 0 Metric Tons Direct Emissions -119.1 Tons/yr Decarbonized
Turnkey Gross Project CAPEX $0 (Existing Plant) / $65,000 New $357,500 (Skid + W2W + Piping) +$292,500 Clean Tech Premium
IRA Section 48 ITC + Utility Grants $0 -$188,000 (40% ITC + $45k Grant) 52.6% Subsidized Capital
Net Capital Outlay (Post-Incentive) $65,000 (Boiler Baseline) $169,500 +$104,500 Net Investment
20-Year Net Present Value (NPV @ 6%) Baseline Reference +$141,600 IRR: 19.8%
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💡 Commercial Wastewater Heat Recovery (WHR) Engineering Insights
Why is raw sewage and greywater the ultimate heat pump source?
Air-source heat pumps struggle in freezing winter weather because outdoor air drops to 0°F to 20°F, dropping COP to 2.0 or lower. Wastewater, by contrast, enters the sewer at 65°F to 75°F (18°C–24°C) year-round due to hot showers, dishwashers, laundries, and indoor ambient sinks. Because the evaporator temperature remains high, water-to-water heat pumps run at unprecedented seasonal COPs between 4.5 and 5.8 regardless of outdoor blizzards.
How does solids separation prevent heat exchanger clogging?
Commercial WHR systems (such as SHARC Energy or Huber) employ automated self-cleaning wedge-wire or macerating rotary screens located upstream of the heat exchangers. The screen extracts wastewater liquids while macerating or deflecting solids back into the sewer downstream, allowing unobstructed hydronic flow through wide-gap shell-and-tube or plate heat exchangers.
Does Wastewater Heat Recovery qualify for the 30%–50% IRA Section 48 ITC?
Yes. Under Section 48 of the Internal Revenue Code (as amended by the Inflation Reduction Act), thermal energy networks and geothermal ground/water heat pump property qualify for the 30% Investment Tax Credit (ITC) if prevailing wage and apprenticeship standards are met, with 10% domestic content and 10% energy community bonuses potentially elevating total tax credits to 50% (or direct pay under Section 6417 for non-profits and municipalities).