Passive Solar

Generation potential is estimated from the same location climate record used for the heat-loss and passive-solar analysis: monthly mean daily global horizontal irradiation and monthly mean air temperature normals for the selected city. Latitude sets the solar geometry used to transpose horizontal irradiation onto the tilted array plane, and the monthly temperature normals drive the cell-temperature derate. Because monthly normals are used, year-to-year weather variation, short-term cloud behaviour, snow or dust events and local micro-climate effects are not represented.

• Array area is the plan area of the roof multiplied by the coverage percentage entered by the user; no allowance is made for penetrations, plant, walkways, fire access or setbacks unless the coverage figure already accounts for them.
• Installed capacity is the array area multiplied by the module efficiency at standard test conditions (1,000 W/m2, 25 °C cell, AM1.5).
• Plane-of-array irradiation is derived from the same monthly climate record used elsewhere in this report: monthly mean daily global horizontal irradiation is split into beam and diffuse with the Erbs correlation, projected onto the array plane over the representative (mid-month) day, and combined with isotropic sky diffuse and ground-reflected components (ground reflectance 0.20).
• Cell temperature is estimated from the monthly mean air temperature plus a Ross-model irradiance rise, and applied with a -0.38 %/K power temperature coefficient typical of crystalline silicon.
• The performance ratio covers inverter conversion, DC and AC wiring, soiling, mismatch, and availability. Any additional array shading loss entered is applied on top of the performance ratio.
• Generation is reported as annual AC energy at the inverter output in the first year of operation. Module degradation (typically 0.4-0.6 %/yr) and inverter replacement are not modelled.
• The offset percentage compares annual generation with the modelled building electricity use (heating and cooling energy after the entered COPs, plus an estimate of other electrical loads from the internal gain density). It is an annual net balance and does not imply hourly self-sufficiency.
• The self-consumption split assumes no battery storage and a typical daytime load profile; actual self-consumption depends on occupancy and tariff structure.

Solar generation disclosure: the photovoltaic figures in this report are indicative estimates produced by a simplified monthly steady-state model using typical climate normals, user-entered roof area and coverage, and generic module and system assumptions. They are not a measured result, a system design, a yield guarantee or a financial forecast. Actual generation will differ - potentially materially - because of weather variation, roof geometry and obstructions, near and far shading, module and inverter selection, string layout, orientation and tilt as built, soiling, temperature, degradation, outages, curtailment, metering arrangements and network or regulatory constraints. No warranty, express or implied, is given as to accuracy or fitness for purpose. Obtain a site-specific design and yield assessment from a qualified solar installer or engineer, and independent financial advice, before making any investment decision.