Source
doi:10.1109/ACCESS.2022.3195242 — original publication (opens in a new tab; the file is not redistributed)
Domain: d01_renewable_energy_storage · SSI: i07_fulfilment_basic_needs, i01_financial_economic_sufficiency
Summary
Models two configurations for an 8-house energy community (Austin, TX measured residential data): (Case I) each house with individual 10 kWh thermal energy storage (TES); (Case II) all houses sharing a single common TES. Demonstrates that a smaller shared TES (22.5–40 kWh) outperforms 80 kWh of distributed individual storage on annual zero-grid-transition hours, 5-year accumulated costs, and payback period. Mechanism: excess PV electricity heats a shared stratified water tank via direct heating mode; demand response optimisation minimises combined grid import cost and foregone export revenue across all 8 houses simultaneously. Austin, TX context; treat pooling principles as structural benchmarks — not absolute NZ targets.
Key claims
- Architecture: 8 houses, each with own PV panels; Case I = individual 10 kWh TES per house (80 kWh total distributed); Case II = single shared TES for all 8 houses. Community objective minimises combined grid import and export across all houses over 8,760 hours. LIT_006
- Storage sizes tested: 22.5 kWh, 25 kWh, 30 kWh, 40 kWh shared TES — equivalent to 450–800 litre hot water tanks. Sizes above 40 kWh tested but show negligible further saving. LIT_006
- Self-sufficiency result (Table 1) — annual hours of zero grid transition:
| Case | Hours (zero grid transition/year) |
|---|---|
| Reference (8 × 10 kWh individual) | 5,319 |
| Common storage 22.5 kWh | 6,950 |
| Common storage 25.0 kWh | 6,960 |
| Common storage 30.0 kWh | 6,970 |
| Common storage 40.0 kWh | 6,979 |
Any common storage size increases zero-grid hours by ~1,630–1,660 hours/year (+31%) vs. individual reference. Diminishing returns above 22.5 kWh. LIT_006
- Payback period (Table 2) — community storage vs. individual storage:
| Case | Payback (r=0.2) | Payback (r=0.3) |
|---|---|---|
| Reference (individual 8 × 10 kWh) | 2.5 years | 3.6 years |
| Common 22.5 kWh | 1.8 years | 1.6 years |
| Common 25.0 kWh | 1.74 years | 1.54 years |
| Common 30.0 kWh | 1.7 years | 1.5 years |
| Common 40.0 kWh | 1.6 years | 1.4 years |
Community shared storage pays back 0.7–2.2 years faster than individual storage across all discount rates (20–30%). LIT_006
- 5-year accumulated cost (Figure 6): Community 40 kWh model reduces total 5-year energy + investment cost to ~€23,000 vs. reference case ~€26,000 for 8 houses — net saving of
€3,000 (€375/household) over 5 years. LIT_006 - Implied investment cost advantage (Figure 6, inferred): Since annual per-household energy costs change minimally across all cases (Figure 5), the majority of the ~€3,000 five-year cost advantage for the community model is attributable to lower investment cost for shared vs. distributed storage. Absolute investment cost (€) per configuration is not itemised in the paper; annual savings (Sa) would be required to back-calculate from the NPV formula (Eq. 13): S = [(1+r)^n − 1] / [r(1+r)^n] × Sa. LIT_006
- Implied minimum viable shared size: Community storage sizes 22.5–40 kWh yield near-identical self-sufficiency gains (Table 1: 6,950 vs. 6,979 zero-transition hours). The 22.5 kWh minimum size (450 litres) likely represents the best cost-per-unit-of-improvement point; larger shared storage adds marginal benefit above this threshold. LIT_006
- Annual energy costs: Per-household annual energy costs change minimally under community model — some houses see reduction, some minor increase; individual variation, but no significant aggregate change. Minor cost increases are acceptable given the investment cost reduction. LIT_006
- Export price asymmetry: Selling price for exported PV electricity ≈ 1/3 of purchasing price — quantifies the financial asymmetry that makes self-consumption through shared storage economically superior to grid export at small community scale. LIT_006
- DHW sizing reference: A 190-litre residential hot water tank provides ~73% of the 8.3 kWh average daily residential water heater demand (Ecotope, 2014, cited as [37]). LIT_006
- Mechanism: Excess PV generation heats shared stratified water tank (direct heating mode); demand response control minimises grid import cost and lost export revenue simultaneously across all community members. LIT_006
Research targets
Documents to retrieve
- [RT_001] Energy Trust (2017) Electric Water Heaters as Grid Energy Storage — likely contains hardware cost benchmarks for 450–800L hot water tanks (€/litre or $/kWh). Cited as [38] in this paper. → D01, D03, I01
- [RT_002] Doroudchi et al. (2018) Approaching Net Zero Energy Housing via EV Charging (Sustainable Cities and Society) — prior work by same research group; may contain CAPEX data for the same community energy system setup. doi:10.1016/j.scs.2018.01.042; cited as [39] in this paper. → D01, I01
Research gaps
- [RT_003] NZ hot water cylinder CAPEX (300–400L, community-scale shared tank) — NZD pricing required for NZ recalibration of the payback periods (Table 2) and 5-year cost findings (Figure 6). The implied ~€375/household net 5-year saving is Austin, TX data; NZ retail pricing (≈ NZD $1,500–3,000 for 300–400L) and tariff structure differ. → D01, D03, I01
- [RT_004] NZ export buyback rate — the paper uses selling price ≈ 1/3 of purchasing price (Austin, TX grid). NZ buyback rates (typically 8–12 c/kWh vs. 28–35 c/kWh import) imply a ratio of 1/3–1/4, broadly consistent — but should be confirmed against current NZ retailer feed-in tariffs before applying the financial model to Neobiome design. → D01, I01
Feeds
- D01 — Shared TES as community energy architecture component; pooling principle (22.5 kWh shared > 80 kWh distributed); zero-transition hours metric; diminishing returns above minimum viable shared size
- I07 — DHW provision from shared thermal store; +31% zero-grid-transition hours; 190L/73% DHW sizing reference
- I01 — Payback 1.4–1.8 yr (community) vs. 2.5–3.6 yr (individual); 5-year cost saving ~€3,000/8 houses; implied investment cost advantage; export price asymmetry
Connections
Links to
SSI indicators (2): I01: Financial & Economic Self-Sufficiency · I07: Fulfilment of Basic Needs
EDT domains (1): D01: Renewable Energy & Storage Systems
Referenced by
SSI indicators (2): I01: Financial & Economic Self-Sufficiency · I07: Fulfilment of Basic Needs
EDT domains (1): D01: Renewable Energy & Storage Systems