# Status of BIPV and BAPV System for Less Energy-Hungry Building in India--A Review
## 5 Perspective and Discussion
### Future Pathway of BIPV/BAPV in India  
Weak BIPV implementation and national planning, lack of energy policy and details of BIPV products, fewer BIPV experts and market professionals are the key responsible factors for slow or no progress of BIPV, for less-energy hungry building in India. The Indian Central government should motivate and support deployment of BIPV research and development by removing non-economic issues to BIPV uses, creating building codes for BIPV integration in building assembly. New training programs related to BIPV can educate the builders, developers, and engineers. Support from central or state-level government organizations, such as NISE, SECI, NIWE, MNRE, IIT, NITs and the state nodal agencies should work together. Windows are one of the weakest components in a building. It allows external heat to come inside (enhance the air condition load), internal heat to outside (enhance heating load) and offer visual connection to building interior to exterior [172; 173; 174; 175; 176; 177; 178; 179; 180; 181; 182; 183; 184; 185]. Building window systems are affected by an overall heat transfer coefficient (_U_-value) and solar energy transmittance (g-value) [186; 187; 188; 189]. For warmer place, high _U_-value and low g-value are required, while for colder area, low _U_-value and high g-value are suitable. Generally, single pane glass possesses higher _U_-value (_U_-value 3-5 W/m\({}^{2}\)K) and higher g-value followed by double (_U_-value-2-3 W/m\({}^{2}\)K g-value lower than single glass) and triple (_U_-value \(<\) 2W/m\({}^{2}\)K; g-value lower than single and double) glass window [190; 191; 192; 193]. This clear and highly transparent window is not able to limit the heat entering from exterior ambient of buildings. Thus, building interior temperature often crosses over occupants' comfort limit (thermal comfort temperature 18-20 \({}^{\circ}\)C). Hence, in order to maintain thermal comfort level, an excessive amount of grid power is consumed to run air-condition (AC). Integration of PV system into the single or double glass can create a single glass BIPV window or double glass BIPV window, which will, not only generate benevolent electricity, but also contro heat and restrict its flow into the exterior, where required, as shown in Figure 9. Semitransparent c-Si PV based BIPV windows can reduce 5.3% heating and cooling load compared to standard BIPV [194] and has ability to limit up to 65% in total heat gains compared \begin{table}
\begin{tabular}{|p{113.8 pt}|p{113.8 pt}|p{113.8 pt}|} \hline
**Product** & **Availability in Research Paper** & **Reference** \\ \hline BIPV window & \(\times\) & \\ \hline BIPV foil & \(\times\) & \\ \hline BIPV tile & \(\times\) & \\ \hline BAPVT (water/air) & \(\checkmark\) & [168; 169] \\ \hline BIPV/BAPV-(PCM) & \(\checkmark\) & [170; 171] \\ \hline BIPV/BAPV-LSC & \(\times\) & \\ \hline BIPV/BAPV-CPC & \(\times\) & \\ \hline \end{tabular}
\end{table} 
Table 3: Availability of BIPV/BAPV products in India. to traditional clear glass [195]. Previous investigation of BIPV window in cooling load dominated climate such as Singapore, Hongkong showed a positive impact on load reduction [196; 197; 198]. In India, buildings' AC load is excessively high, due to thehigh g-value of window. In summer, buildings' windows are closed, in order to abate hot air and sunlight [199; 200]. This also creates a dearth of light in an indoor setting, which encourages occupants to employ artificial light. Small-to-medium office buildings use air conditioners during the day and peak summer, and are not in use at night or off-peak season. Hence, advanced single or double glass-based semitransparent BIPV window systems, which possess lower g-value compared to clear glass, are favorable in India as they can be particularly be influential in limiting excess usage of AC and lighting load for a less-energy hungry building.The inclusion of this semi-transparent BIPV window, not only lowers the g-value, but allows sufficient daylight and generates benign electricity concomitantly.