The lifespan of building roofs

光伏電站需要運營25年，一般要8-10年左右才能收回全部成本，在項目開發(fā)時，需要了解屋頂能使用的年限，年限太短不適宜進行開發(fā)，一般要超過20年。

Photovoltaic power plants require 25 years of operation, usually around 8-10 years to recover the full cost. During project development, it is necessary to understand the lifespan of the roof. If the lifespan is too short, it is not suitable for development, usually exceeding 20 years.

建筑屋面荷載

Building roof load

屋面荷載分為恒荷載和可變荷載。恒荷載是指結(jié)構(gòu)自重及灰塵荷載等，光伏電站需要運營25年，其自重屬于恒荷載。通常鋼結(jié)構(gòu)廠房上裝光伏系統(tǒng)每平米會增加15公斤的重量，磚混結(jié)構(gòu)廠房的屋頂每平米會增加80公斤的重量。可變荷載是考慮狀況下暫時施加于屋面的荷載，分為風(fēng)荷載雪荷載地震荷載活荷載等。

The roof load is divided into constant load and variable load. Dead load refers to the self weight of the structure and dust load. Photovoltaic power plants require 25 years of operation, and their self weight belongs to dead load. Usually, installing a photovoltaic system on a steel structure factory building adds 15 kilograms of weight per square meter, while the roof of a brick concrete structure factory building adds 80 kilograms of weight per square meter. Variable load refers to the load temporarily applied to the roof under consideration, which is divided into wind load, snow load, seismic load, live load, etc.

建筑用電量及用電價格

Building electricity consumption and electricity prices

工商業(yè)光伏發(fā)電投資價值高，重要的是工商業(yè)電價高，如一般工商業(yè)高峰電價是1.15元/度，自發(fā)自用比例高，一般工商業(yè)高峰時段是8：00~22：00，這個時段和光伏發(fā)電基本同步。因此要統(tǒng)計建筑物的用電情況，有一些企業(yè)用電量大，如大型商場寫字樓車站碼頭等商業(yè)區(qū)。

The investment value of industrial and commercial photovoltaic power generation is high, and what is important is the high electricity price of industrial and commercial industries. For example, the peak electricity price of general industrial and commercial industries is 1.15 yuan/kWh, and the proportion of spontaneous self use is high. The peak hours of general industrial and commercial industries are from 8:00 to 22:00, which is basically synchronized with photovoltaic power generation. Therefore, it is necessary to calculate the electricity consumption of buildings. Some enterprises have high electricity consumption, such as large shopping malls, office buildings, stations, docks, and other commercial areas.

化學(xué)原料制品非金屬礦物制品黑色金屬冶煉和有色金屬冶煉模具加工熱處理電鍍等工廠，這些高能耗企業(yè)同時也非常需要光伏發(fā)電來降低它的能耗指標(biāo)。但也有一些企業(yè)用電比較少，如物流園倉儲等，這些建筑往往面積很大，但本身沒有什么設(shè)備，用電量很少，安裝光伏后只能大部分上網(wǎng)賣電，也不適合投資。

Chemical raw material products, non-metallic mineral products, black metal smelting, and non-ferrous metal smelting, mold processing, heat treatment, electroplating and other factories. These high-energy consuming enterprises also greatly need photovoltaic power generation to reduce their energy consumption indicators. But there are also some enterprises that use relatively little electricity, such as logistics parks and warehouses. These buildings often have a large area, but they do not have much equipment and use very little electricity. After installing photovoltaics, most of them can only sell electricity online, which is not suitable for investment.

建筑物內(nèi)的電網(wǎng)質(zhì)量

Quality of power grid inside buildings

光伏逆變器

Photovoltaic inverter

向電網(wǎng)輸送電能，電網(wǎng)質(zhì)量的好壞也會對逆變器產(chǎn)生影響，在一些機械加工廠，有吊車電焊機龍門銑床等大功率設(shè)備，和一些電弧爐等設(shè)備開，在啟動和關(guān)斷之間，電能變化非常劇烈，電網(wǎng)來不及調(diào)整，同時伴隨大量的諧波，電網(wǎng)中存在的諧波和不平衡負序分量將導(dǎo)致光伏系統(tǒng)輸出有功功率波動。由于光伏逆變器輸出都是有功功率，如果建筑物內(nèi)有些設(shè)備需要無功功率，只能由電網(wǎng)來提供，因此當(dāng)光伏系統(tǒng)工作時，有可能造成企業(yè)無功功率超標(biāo)，力調(diào)電費增加的事情發(fā)生。

The transmission of electrical energy to the power grid can also have an impact on the quality of the inverter. In some mechanical processing plants, high-power equipment such as cranes, welding machines, gantry milling machines, and some electric arc furnaces are turned on. Between startup and shutdown, the changes in electrical energy are very drastic, and the power grid cannot be adjusted. At the same time, a large number of harmonics and unbalanced negative sequence components in the power grid will cause fluctuations in the output active power of the photovoltaic system. Due to the fact that the output of photovoltaic inverters is all active power, if some equipment in the building requires reactive power, it can only be provided by the power grid. Therefore, when the photovoltaic system is working, it may cause the reactive power of the enterprise to exceed the standard and increase the power regulation electricity bill.

質(zhì)量較差的地方安裝光伏系統(tǒng)，需要增加電能質(zhì)量改正的設(shè)備，如有源濾波器APF,靜止無功發(fā)電器SVG等，并對這些設(shè)備和電網(wǎng)的參數(shù)進行實時監(jiān)控。逆變器的并網(wǎng)點盡量遠離用電設(shè)備，如直接升壓到中壓10kV并網(wǎng)，可以回避諧波等電能質(zhì)量風(fēng)險。

Installation of photovoltaic systems in areas with poor quality requires the addition of equipment for power quality correction, such as active power filters (APFs) and static reactive power generators (SVGs), and real-time monitoring of these equipment and grid parameters. The grid connection point of the inverter should be as far away from the electrical equipment as possible, such as directly boosting to the medium voltage 10kV grid connection, which can avoid power quality risks such as harmonics.

配電設(shè)施及并網(wǎng)點

Distribution facilities and connection points

配電設(shè)備是光伏電站選擇并網(wǎng)方案的根據(jù)之一，主要考查內(nèi)容有廠區(qū)變壓器容量數(shù)量母聯(lián)負荷比例等。

Distribution equipment is one of the basis for selecting grid connection schemes for photovoltaic power stations, mainly examining the capacity, quantity, and load ratio of transformers in the factory area.

雖然新標(biāo)準(zhǔn)取消了光伏容量要小于變壓器容量百分之25的限制，而且還沒有規(guī)定上限是多少，但是根據(jù)經(jīng)驗，當(dāng)光伏容量超過變壓器容量百分之70時，工廠內(nèi)電能質(zhì)量會下降很多，因此建議光伏容量不要超過變壓器容量百分之70。

Although the new standard has abolished the limit of 25% less photovoltaic capacity than transformer capacity, and has not yet specified the upper limit, based on experience, when photovoltaic capacity exceeds 70% of transformer capacity, the power quality in the factory will decrease significantly. Therefore, it is recommended that photovoltaic capacity not exceed 70% of transformer capacity.

工商業(yè)可選擇單點并網(wǎng)和多點并網(wǎng)，各有好處，單點并網(wǎng)是集中在一起，便于管理，多點并網(wǎng)是多個地方就近并網(wǎng)，交流線路短，效率高?？筛鶕?jù)實際情況來選擇。

Industry and commerce can choose between single point grid connection and multi-point grid connection, each with its own advantages. Single point grid connection is centralized and easy to manage, while multi-point grid connection is connected to multiple nearby places, with short communication lines and high efficiency. You can choose according to the actual situation.