What Should You Know Before Installing Solar Panels on Commercial Buildings
Commercial installation primary ensure roof per square meter bearing capacity exceeds 20 kilograms.
Suggest retrieve enterprise near one year electricity usage peak value data to customize system capacity, thereby precisely offset high commercial electricity price, usually 4 to 6 years then can completely recover investment cost.
Roof Capacity
Calculate calculate has how heavy
The standard commercial photovoltaic module's size is usually 2.2 meters long, 1.1 meters wide, and every piece weighs precisely 28.5 kilograms. Aluminum alloy installation bracket will take overall weight distribution, per square meter only increases 3.5 kilograms's extra burden.
On a 2000 square meters' flat roof, 500 pieces of solar panels composed of an array will produce a total of 14250 kilograms' constant downward pressure weight. In order to prevent equipment inside sliding, no need to punch holes' ballast system needs extra place counterweight, per square meter will increase 18 to 32 kilograms's concrete blocks. Original building design blueprint on marked's usable live load if lower than 30 kilograms/square meter, this set equipment installation scheme in applying for a construction permit stage will have a 90% probability of being rejected by the local building department.
l Factory internal supporting roof's 6 meters long H-type steel beam, in full load state under middle position's maximum allowed physical deflection cannot exceed 20 millimeters.
l Encounter winter snowfall amounts exceed 50 centimeters's northern region, accumulated snow will in long reach 3 months's time inside give roof increase per square meter 120 kilograms to 180 kilograms's temporary snow load.
l Solar panel, metal bracket, and 20 centimeters thick accumulated snow's comprehensive weight superimposed together, will let the roof surface's total pressure-bearing index instantly break through per square meter 200 kilograms.
l Towards bearing capacity insufficient's old factory, construction team needs to consume 14 days to 21 days' time to conduct steel structure reinforcement. This item's engineering budget unit price fluctuates between 12 dollars and 18 dollars per square foot.
Pick installation bracket
Installation workers will use this kind of flat roof on a tilt angle of 10 degrees or 15 degrees's bracket, take afternoon 2 o'clock to 4 o'clock's sunlight absorption rate elevate 12%. Metal standing seam roof's metal raised seam spacing is generally divided into 40.6 centimeters or 61 centimeters two kinds of standard specifications. Aluminum clamp directly bites on metal seam, realizes 0 roof penetration holes, at the same time, a single clamp can resist 1.2 kilonewtons's upward pulling force. A skilled worker installing one of these kinds of clamps only needs 2.5 minutes, compared to the traditional punch hole installation mode, saved 40% labor hours.
l Concrete material's flat roof needs to use mechanical anchor bolts, through electric drill deep into concrete floor slab internal 10 centimeters conduct fixing.
l Every installation of a 100 kilowatt capacity photovoltaic system needs 350 to 400 fixed anchor points on a cement roof surface.
l Building inspector will randomly extract 5% anchor points and use a pulling tester to conduct inspection. Instrument panel's anti-pulling resistance reading must reach per root bolt 1500 pounds then count as qualified.
l Tilt angle reaches 30 degrees's pitched roof, rainwater flow speed high reaches per second 2 meters, needs to use waterproof gasket's L-type supporting foot to raise solar panel high 15 centimeters, to maintain bottom air circulation and take module operation temperature lower 5 degrees Celsius.
Block big wind
Building edge periphery 3 meters's region, bears's gust wind pressure is roof surface center region's 2.5 times. When extreme weather causes wind speed to reach 180 kilometers per hour, a single piece photovoltaic panel's upward suction force will soar to 1400 Pascals. The installation team will face every row's north side, using screw fix on a thickness of 0.8 millimeters's galvanized steel wind deflector. This kind conforms to aerodynamic design's wind blocking device, can take wind force produced's lift coefficient massively lower 65%. In the distance coastline, 50 miles range inside the strong wind region, building code compulsorily requires roof equipment must resist 2400 Pascals's extreme wind pressure.
l Construction party needs to take every piece panel's bottom horizontal support aluminum guide rail from standard's 2 roots to 3 roots.
l Bracket and roof connection point's span spacing will also shorten from conventional's 1.2 meters to 0.8 meters, to increase overall structure's stiffness.
l Increased hardware accessories will let total equipment procurement budget per watt rise 0.12 dollars, but panel by crazy wind blown flying's probability will lower to 0.01%.
l Installed on floor height exceeds 15 meters, roof on's system, every year needs to accept 1 time wind tunnel simulation data's re-calibration, ensure fastener's torque value maintains at specified's 20 Newton meters above.
Anti-water leakage test
Capacity is 500 kilowatts's large scale system on roof surface will produce exceeds 1200 punching penetrations. The worker will use a size of 20 centimeters, multiply 20 centimeters's metal waterproof flashing board cover hole, and at the bottom lay a thickness of 3 millimeters's butyl waterproof tape. Hit on bolt head's polyurethane sealant at 20 degrees Celsius's air temperature needs 24 hours to completely cure. This kind of chemical colloid in strong ultraviolet ray's continuous irradiation under, long reaching 15 years's time inside all can maintain 98% above's material elasticity.
l Possess 20 years warranty period's commercial roof if still in warranty period inside, photovoltaic installation company must pay per hour 150 dollars to 250 dollars's fee, hire original factory certified roof contractor come to scene supervise.
l Refuse to use certified contractor, will let remaining 12 years's waterproof factory warranty contract in drill down first hole's 3 seconds inside automatically become invalid.
l In system installation complete and experience first field rainfall amount exceeds 50 millimeters's big rain after, testing personnel will manipulate with thermal imaging lens's drone ascend to 30 meters's height conduct scanning.
l Infrared camera can keenly capture 0.5 degrees Celsius's temperature difference change, in 48 hours, inside accurately calibrate out coil material below accumulated water's specific area and coordinates.
Still can use how many years
A set total cost of 300,000 dollars' photovoltaic system will continuously generate electricity for 25 years to 30 years. Assume the current commercial roof has already been used for 12 years, then the roof's waterproof layer's remaining safe usage lifespan is only 8 years to 13 years. In a photovoltaic system, it operates for 10 years, for repaving leaking roofs and dismantling 700 pieces of solar panels, the enterprise needs to pay 30,000 dollars to 45,000 dollars' secondary dismantle install labor fee. Equipment shutdown waiting for roof refurbishment cycle long reaches 3 to 4 weeks, in this period, the factory will lose about 4,000 dollars's electricity bill saving revenue.
l Thoroughly eradicate and re-pave 2000 square meters' commercial roof, initial material and labor fee high reaches 120,000 dollars to 180,000 dollars.
l Take roof refurbishment schedule move forward, with solar panel's enter scene installation date arrange in same 1 month inside, can enterprise save 15% to 20% scaffolding build and heavy machinery lease fee.
l A unit lifting a 50-ton mobile crane's daily lease price is 2000 dollars. It can simultaneously take into rolls' waterproof material and heavy reaching 15 tons' solar panel tray together hoist to 20 meters high's roof.
l Coordinate construction can take factory load unload cargo region's logistics congestion time from original's 25 days to 14 days, guarantee every day 80 units freight truck's enter exit efficiency drop amplitude not exceeds 5%.
Energy Demand
Read and understand electricity bill
Commercial power company's billing system usually takes 15 minutes as one data collection cycle, and the whole day, 24 hours, will generate 96 power readings. Long-reaching 12 months to 24 months' history bill inside, hiding kilowatt-hours (degrees) and kilowatts (demand) two completely independent pricing dimensions. One home occupying an area of 50,000 square feet's manufacturing factory, every month's actual total power consumption amount may fluctuate between 150,000 kilowatt-hours up and down. The energy electricity bill's unit price usually maintains at per kilowatt-hour between 0.08 dollars and 0.12 dollars.
Bill amounts of 40% to 60% often originate from demand electricity bills, according to current month's single-time 15-minute highest peak power to double charge. Local public utility company's demand unit price will be set at per kilowatt 15 dollars to 25 dollars, varying by high position. As long as the whole month has any one 15 minutes' average power soared to 500 kilowatts, the current month's demand electricity bill will be fixed at 7,500 dollars to 12,500 dollars. Install solar panels before must month by month calculate peak power's appear time period, usually concentrates at summer afternoon 2 o'clock to afternoon 5 o'clock's high temperature time period.
Billing item name | Pricing unit | Estimated unit price interval | Occupy total bill proportion | Calculation frequency |
Basic service fee | Every month/account | $50 - $150 | 1% - 3% | 1 time/month |
Energy electricity fee | Kilowatt-hour (kWh) | $0.08 - $0.12 | 40% - 50% | Continuously accumulate |
Peak demand fee | Kilowatt (kW) | $15.00 - $25.00 | 40% - 60% | 15 minutes peak value |
Power factor penalty | Percentage (%) | $0.50 - $2.00/kVAR | 0% - 5% | Lower than 90% trigger |
Catch power consumption big user
HVAC system occupies the whole building's commercial building's total power consumption load's 35% to 45%, a unit 50 tonnage's commercial central air conditioning unit at start instant will produce exceeds 300 amperes's instantaneous inrush current. Continue time only is 3 seconds to 5 seconds's start current, will take whole building's instantaneous electricity usage demand push high 120 kilowatts to 150 kilowatts. Industrial grade air compressor's motor nameplate rated power usually is 75 kilowatts, in equipment add air build pressure's 8 minutes cycle inside, load rate will always maintain at 95% above.
Factory assembly line's injection molding machine or large-scale stamping equipment operates two shifts every day, totaling 16 hours, occupying an area of only 20 square meters's equipment region can consume the whole factory's 18% electricity amount. Take cold storage's setting temperature from minus 20 degrees Celsius upward to minus 18 degrees Celsius, compressor's operating time every day can be reduced by 1.5 hours, single month saved electrical energy high reaches 4500 kilowatt-hours. Photovoltaic inverter needs to configure precise smart meter, with 250 milliseconds' sampling frequency, real-time track factory area load's fluctuation amplitude.
Calculate electricity usage curve
Solar array's power generation amount presents a parabola shape, from morning 11 o'clock to afternoon 2 o'clock between 3 hours, producing the whole day's power generation total amount's 65%. Capacity is 300 kilowatts's roof photovoltaic system in clear cloudless noon time, actual output power can stabilize at 250 kilowatts to 275 kilowatts between. Due to sunshine angle deflection, arrived at 4:30 p.m., photovoltaic system's output power will cliff-style drop to the highest peak value's 25% below.
Commercial buildings' electricity usage peak often will from afternoon 3 o'clock continuously extend to night 7 o'clock, producing a long-reaching 4-hour supply demand mismatch period. In states that do not have net energy metering policies, daytime generated electricity can only be transmitted back to the power grid and obtain per kilowatt-hour 0.03 dollars to 0.05 dollars's wholesale price compensation. Daytime towards power grid low price reverse flow 500 kilowatt-hours electricity amount, night again with per kilowatt-hour 0.15 dollars's retail price buy back, one go one return will produce 50 dollars's financial price difference loss. System capacity design needs to stick at building daytime lowest basic load's 85% around, ensure daytime photovoltaic generated electricity amount 95% above all can be completely digested by the factory.
Plan configure energy storage
The capacity is 200 kilowatts/400 kilowatt-hours' industrial grade lithium iron phosphate cell pack, hardware procurement and on-site debug's special budget needs about 180,000 dollars to 220,000 dollars. Energy storage system can in the power grid peak period provide long-reaching 2 hours' full power discharge, take factory towards power grid demand's peak power abruptly press low 200 kilowatts. According to per kilowatt 20 dollars's demand electricity bill standard calculate, cell pack single month then can cut 4,000 dollars's bill expenditure, whole year's demand electricity bill save quota high reaches 48,000 dollars.
Commercial lithium cell's cycle lifespan index currently generally can reach 6000 times complete charge discharge, according to every day 1 time charge discharge's frequency, physical usage limit long reaches 16.4 years. Cell pack internal's chemical conversion will produce heat energy loss, leading to system's charge discharge round-trip efficiency usually maintaining at 88% to 92% interval. In order to maintain the cell cabin inside a constant 25 degrees Celsius operation environment, liquid cooling temperature control system every year needs extra consume 3000 kilowatt-hours to 5000 kilowatt-hours's electricity amount.
Energy storage system parameter | Numerical index | Financial impact | Operation and maintenance requirement |
Charge discharge efficiency | 88% - 92% | Every loss 10% electricity amount increases $0.015/degree hidden cost | Every year calibrate cell management system (BMS) |
Cycle lifespan | 6000 - 8000 times | Depreciation amortization period extended to 15 years | Maintain depth of discharge (DoD) at 80% inside |
Demand peak shaving ability | 100 kW - 500 kW | Every month save $1,500 - $12,500 demand fee | Millisecond level response speed test |
Capacity degradation rate | Every year 1.5% - 2% | 10th year usable capacity remaining 80% | Every half year, conduct 1 time 100% full charge full discharge test |
Leave out expansion amount
Enterprise replace pure electric delivery fleet or install employee charging pile, will in future 3 years to 5 years thoroughly change current electricity usage base. A unit ordinary's Level 2 AC charging pile output power is 7.2 kilowatts, and simultaneously for 10 units of electric vehicles charging will increase 72 kilowatts's constant load. A unit DC fast charging pile's nominal power is even high, reaching 150 kilowatts to 350 kilowatts, a single unit equipment can then let the factory's original peak electricity demand double up one time.
Natural gas boiler transform to commercial air source heat pump, every produces 1 million British Thermal Units (BTU) of heat, needs to consume about 85 kilowatt-hours's electrical energy. In phase one, photovoltaic engineering inside extra reserve 20% inverter capacity and roof wiring cable tray, current's per watt marginal increase cost only is 0.15 dollars. Wait three years after again independently bid to expand 50 kilowatts' photovoltaic array, due to need re-pay personnel enter scene, crane lease and permit approval fee, single watt comprehensive construction cost will soar to 2.6 dollars above.
Compliance
Take building permit
A complete application dossier thick reaches 50 pages to 100 pages, covers the structure engineer's single-line diagram, three-line diagram as well as equipment data sheet. Municipal review personnel will be inside next 4 weeks to 8 weeks, reviewing DC side voltage whether it breaks through 1000 volts' upper limit, AC side circuit breaker amperage whether with inverter maximum continuous output current's 125% match. Encounter installed capacity reaches 500 kilowatts's large-scale roof array, first round blueprint by returned require rectify's probability high reaches 60%.
Review blueprint's every one red pen annotation, all will let the engineering team extra consume 14 days to 21 days' waiting cycle to re-submit document. Encounter roof structure exists large span no support region's old industrial factory. Reviewer will compulsorily require supplement submit one copy long reaching 20 pages' dynamic wind load three-dimensional simulation report. Submit this copy by the third party engineering firm's calculation book, will spend enterprise extra's 4,500 dollars to 7000 dollars.
According to "National Electrical Code" (NEC) Article 690's hard regulation, all penetrate commercial building roof's DC cables must thread into rigid metal conduit inside, conduit distance roof surface finish surface's vertical height must not be lower than 20 centimeters. Conform to specification's construction method can prevent cable long term soak in 5 centimeters to 10 centimeters deep's roof accumulated water inside, avoid trigger insulation layer aging peel off as well as single point towards ground leakage fault.
Leave out fire lane
Length width size exceeds 50 meters' commercial roof, its four sides edge must permanently reserve width reaches 1.8 meters' obstacle-free fire lane. Array internal every interval 45 meters then needs cut out one strip width 1.2 meters's horizontal or vertical corridor, for fully armed firefighters to execute roof smoke exhaust operation time can smoothly pass.
Building tops' gravity smoke exhaust vent surrounding 3 meters radius range inside strictly forbid lay any photovoltaic module, forcefully empty out above-mentioned safety buffer zone, often will let original blueprint's usable installed capacity shrink 8% to 12%. Once the fire department patrol discovers the module edge distance light well's physical distance is only 2.8 meters, even if only missed 0.2 meters, will issue out every day 500 dollars's penalty ticket and order shutdown dismantle cross-boundary equipment.
Rapid Shutdown function is a city-level fire department grid connection acceptance time's one vote veto item. The whole set system must have an emergency stop switch pressed down for 30 seconds countdown inside, take distance photovoltaic array 1 foot range outside, all DC main conductor voltage forcefully drop to 30 volts below, at the same time, system inside between conductors's residual current must not exceed 240 volt-amperes. Value reaches standard then can ensure firefighter use metal fire axe chop open roof structure time, will not encounter fatal high voltage electric shock.
Power grid's rule
Capacity between 250 kilowatts to 1 megawatt range inside medium-large scale commercial projects, usually will trigger local power grid company's level three interconnection review process. Power grid engineers will towards applicants collect 1500 dollars to 5000 dollars's special research fee, spend 60 days to 120 days's time to establish a regional power flow model.
When located block 12 kilovolts distribution feeder on's distributed power source total connection capacity, exceeded this substation's whole grid annual highest peak load's 15% time, the power grid company will issue one copy of an extremely expensive system transformation quotation. The enterprise needs to bear the originally belongs to the power grid asset's line capacity increase expense, take block corner place that unit used 20 years's 500 kilovolt-ampere old transformer upgrade to 1000 kilovolt-amperes.
Give substation facility expand capacity or replace with two-way communication protocol's smart meter, material and construction's labor bill will violently fluctuate between 25,000 dollars and 85,000 dollars. Enterprise if in received quotation after's 30 working days inside did not full amount transfer money, original's interconnection application agreement will immediately become invalid, roof on generated's every degree solar energy electricity all unable to legally input to public distribution grid inside produce revenue.
Land use and zoning
Installed on flat roof's photovoltaic array if adopt tilt angle reaches 15 degrees's conventional bracket, its highest point distance roof surface's vertical drop usually will reach 60 centimeters to 80 centimeters. Part commercial use zoning's planning regulations require roof additional equipment absolutely cannot be higher than the parapet wall's horizontal line.
The engineering team can only compromise and adopt a 5-degree tilt angle's flat paving style installation scheme, causing system overall power generation efficiency to be pulled down by about 4.5% every year. Located at the airport runway 5 miles away, inside the logistics warehouse, install solar panels, must in advance towards the Federal Aviation Administration (FAA) submit highly professional's optical glare analysis test report.
Glare calculation software will simulate all weather 365 days, every interval 1 minute's sun operation three-dimensional trajectory, use digital models to prove glass surface reflected light ray in line of sight elevation angle 50 degrees range inside, per square centimeter's brightness absolutely will not break through 1000 candelas's warning value. Data qualified then can dispel aviation department's doubts, ensure approach landing's commercial flight pilot retina exempt from strong light pollution's interference.
History and environmental protection
Building age exceeds 50 years' commercial building in submitting photovoltaic installation filing time, has 90% probability will by local historic preservation commission require conduct long reaching 3 months to 6 months' special hearing. From the public street or adjacent building eye level direction, the naked eye can capture the solar panel's layout scheme, modify the blueprint's labor and time cost extremely high.
The design team has to take the module entirely towards the roof geometric center line, retreat at least 3 meters to 5 meters, causing 15% to 20% of the lighting to be extremely good in vain wasted. Towards park outdoor parking lot region planned's capacity reaches 800 kilowatts's photovoltaic carport project, early period must issue single copy cost reaches 10,000 dollars to 25000 dollars's rainwater runoff discharge model and soil erosion control plan.
Carport steel structure's underground foundation piling operation will disturb more than 1,000 square meters's surface soil. Civil engineers must at construction sites surrounding set up a height of 60 centimeters's polyester fiber anti-silt fence. In an encounter, continuous rainfall amounts exceed 15 millimeters's bad weather after, construction party wants in 24 hours inside towards environmental protection department's surrounding sewer's water quality sampling test laboratory report, did not submit on time will face a daily highest 25,000 dollars's administrative violation fine.