N
CO
H + CO
Combustion exhaust CO + H O + N
Natural gas CH
H
H O
Carbon capture
Electrolysis
Methanation
H O
Heat
H O
O
Electricity
Figure 2 Carbon Bridge 1000 process flow diagram
• 1 therm = 0.0293 MWh, so total electricity required: 166,666 therms × 0.0293 MWh/therm = 4,883.35 MWh per year. • Since the system operates only 3,650 hours per year (10 hours per day, off-peak only): 4,883.35 MWh ÷ 3,650 hours = 1.33 MW electrical demand. Electrical service upgrade requirement: 1.33 MW. Since natural gas consumption is seasonal, the Carbon Bridge must be able to store CO₂ when heating demand is low for later use. Most of the CO₂ storage can be centralised, with deliveries made during the heating season, reducing the need for large on-site storage. For reference, if 100,000 therms of gas produces 529 tonnes of CO₂, about 33% of this must be stored for non-heating season operation, or 176 tonnes of CO₂. If stored on- site, this would require: • 173.3 cubic metres of storage (equivalent to three NYC rooftop water towers). • 50-atm liquid CO₂ tanks, which are already commercially available. This approach eliminates the need for extra electrolyser capacity and keeps on-site storage requirements manageable, similar to existing oil and propane delivery models. The alternative is direct electrification using an air-source heat pump that requires electricity in real time: • Assume 75% of annual heating occurs in the three coldest months. • Annual heating load: 100,000 therms × 75% = 75,000 therms. • Convert to MWh: 75,000 therms × 0.0293 MWh/therm = 2,198 MWh. • Dividing by operating hours (three months, 30 days/month, 24 hours/day): 2,198 MWh ÷ (3 × 30 × 24) = 1.02 MW base electrical demand.
• When accounting for safety factors, peak demand fluctuations, and reliability needs, the electrical service upgrade must be at least 2 MW. The P2G approach requires 50% less electrical service capacity than a heat pump despite its lower efficiency because it shifts electricity consumption to off-peak hours and relies on stored energy (RNG) for peak heating. P2G and Carbon Bridge quantitative technical overview P2G bridges the gap between intermittent renewable power generation and continuous energy demand, creating a storable, dispatchable fuel that integrates seamlessly into existing natural gas infrastructure. The process (see Figure 2 ) begins by capturing CO₂ directly from combustion exhaust – typically existing natural gas boilers – which is then purified through exhaust gas scrubbing and monoethanolamine (MEA) absorption to yield a high-purity CO₂ stream. Next, the purified CO₂ is subjected to desorption, where it is released from the solvent and concentrated for conversion. The carbon capture and storage process requires about 200 kWh of electricity per tonne of CO₂. This excludes the desorber’s thermal load, which is supplied by waste heat from the downstream methanation process. Simultaneously, electrolysis powered by curtailed or off-peak renewable electricity splits water into hydrogen and oxygen. Standard Carbon employs potassium hydroxide (KOH) alkaline electrolysers, achieving an efficiency of approximately 65-70% (on a lower heating value basis), producing hydrogen critical for the subsequent methanation step. Methanation occurs in a Sabatier reactor,
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