PAT Target, Solar Energy and Boundary Change
A cement grinding unit is a designated consumer under the PAT scheme. Its baseline specific energy consumption is 34.0 kWh/t of cement (gate-to-gate, including grinding, packing and utilities). The current PAT target is a 5% reduction, i.e. 32.3 kWh/t. In the reporting year the unit produced 1.20 million t and consumed 37.2 GWh from the grid plus 2.4 GWh from a captive rooftop solar plant that is behind the plant meter. The unit also wants to exclude 1.8 GWh of packing-plant load that was outsourced mid-year from the boundary. Its total measured energy at the original boundary is 39.6 GWh. Management asks whether it has met the target and how to present the case to the verifying agency.
1. Calculate SEC with and without the proposed exclusions. Which number is defensible, and by how much is the target missed?
Read the worked answer
At the original boundary, SEC = 39.6 GWh/1.20 Mt = 33.0 kWh/t. Target = 34.0 × 0.95 = 32.3 kWh/t; shortfall = 0.7 kWh/t × 1.20 Mt = 840 MWh. If solar is subtracted, SEC = 37.2/1.2 = 31.0 kWh/t, which would falsely show over-compliance; the 2.4 GWh is consumed inside the boundary and cannot be self-excluded just because it is renewable. If the 1.8 GWh packing load is also removed, 37.8/1.2 = 31.5 kWh/t, but that changes the boundary and production; the baseline and target must be restated. If both solar and packing are excluded, 35.4/1.2 = 29.5 kWh/t, even less comparable. The defensible reported SEC is 33.0 kWh/t until the verifier approves a boundary change. Present solar separately as renewable generation and the outsourced load with a restated baseline; do not net them into a claimed 31.0.
2. Propose a 840 MWh gap-closing plan using grinding and utility measures, with priority and evidence.
Read the worked answer
Priority: (1) grinding circuit optimization - separator adjustment, mill internals, feed moisture and avoiding over-grinding; a 2–4 kWh/t saving at 1.2 Mt is 240–480 MWh; (2) compressed-air leak survey and pressure reduction - 5–10% of air energy; (3) pump and fan VFDs on cooling water and baghouse; (4) solar expansion, but it may not count toward SEC unless boundary rules allow. To close 840 MWh, combine at least 400 MWh from grinding, 200 MWh from compressed air, 150 MWh from pumps/fans and 90 MWh from lighting. Meter each before/after, use IPMVP Option B and adjust for cement type and fineness. Do not rely on outsourcing. Present cost and payback; if the gap remains, use the applicable PAT carryover or compliance options.
3. What verification evidence and boundary controls are needed?
Read the worked answer
Provide calibrated meters at grinding, packing, utilities and solar; reconcile to utility bills. Document production by cement type, clinker factor and fineness, plus any boundary change; restate baseline if packing was outsourced. Do not exclude load without a corresponding baseline and throughput adjustment. For solar, show generation and consumption behind the meter, and state its treatment under the scheme; keep it separate from SEC. For each project, keep baseline and post-retrofit data, invoices, commissioning reports and regression adjustments for production and fineness. Have the verifier sign off on the boundary before the reporting year closes; otherwise the 33.0 kWh/t result stands and the 840 MWh shortfall remains.