SMART HOME
:Energy Efficient Building concept in Delhi’s Residential sector
Case study : Delhi’s first Net-Metered Residential 2kWp Solar Rooftop System with BSES Rajadhani
In order to promote energy efficiency at home, a typical family in Delhi is been analysed for their daily life style and practices, connect load, power consumption and areas of improvement.
The family in this study has typical demographic details much similar to an average service class family in Delhi like 5 Members, Adult -3 (Husband, Wife & Mother), Kids-2 (School going, one in Middle one in nursery) living in 2 BHK Home, a typical floor of 100yard.
Since the family needs were growing, they approached a nearby small builder to build a bigger floor for them in a new premises close by.
They wanted to improve on their lifestyle but control on consumption thus need was energy efficiency and to get the design of new building of their floor to be optimised balancing the above.
With this objective and purpose together with the builder this house was to be designed with simplicity achieving energy optimisation taking into account the historical consumption pattern and family need expected to grow in future.
So a typical Energy audit was the first step. Past data of last 5 years of monthly electric bills, average tariff, connected load, daily consumption style for summer and winter etc. was collected.
Sanctioned / Connected Load – 4kW, MDI less than 4kW in last 5 years. Connected Major equipment’s :
1. 2 nos x Window A/c 1.5 ton
10. 1 set x Chimney, Induction, OTG, Mixer, grinder etc. Kitchen appliances
11. 1 no x washing m/c
12. 1 no x invertor 1kVA
At large the annual data indicates about average 8-9 units per day as consumption but the monthly pattern was quite different.
History of daily average consumption plotted for each month to observe the monthly pattern, reveals that needs vary between 4-16 units per day. Needs are maximum in August due to air-conditioning needs. The life style and pattern is analysed to see any improvement.
Since it is a floor shared with co-owners of other floors in the same building, cost was constrained. It was designed to have simple changes making big impact but without increasing the cost. In this new 4BHK, 150 yard floor, following was ensured:
1. Building layout is kept in a way that each area has positive energy respecting Vastu design fundamentals.
2. Interior Design gives feel of larger area and openness across.
3. Maximum possible opening is kept in East &West as North-South is closed walls.
4. Maximise natural light and Cross ventilation using Doors, Windows, Vertical shaft etc. across all 4 bedrooms, drawing- dining, kitchen, bathrooms, staircase so as to have fresh feeling and less dependency on powered light/cooling/heating.
5. Use of natural materials like wood as best feasible, wood finish tiles etc.
6. Energy efficient equipment’s (3-Star AC, 5-Star Geyser, LED lighting etc.)
7. Provision for installing a Solar Rooftop on top (Lift Tower in South)
This new floor was constructed in next 1 year and family shifted into new home in May’14.
Close to 2 years power consumption data reflects that the need for a/c has come down and the maximum daily consumption has reduced. This is significant as the family has moved from a 2 BHK to 4BHK house, lifestyle has improved, needs grown but consumption has not increased.
With the available space on the lift tower top i.e. only 9 sq mt, limits the size of Solar capacity to max 2kWp.
The available data of power consumption from 2010-2014 and prediction for next 1-2 years is plotted to see average energy requirement v/s what a 2kW Solar system can produce.
It is seen that average 8-10 units per day is the power needed and 2kWp Solar System is likely to generate close to this average daily consumption.
Since the most consumption was in non-Solar hours, this hourly solar generation mostly not matches to the hourly power consumption profile.
This challenges that a typical load based off-grid solar system is not the best suited answer.
This starts story of Delhi’s first net-metered residential rooftop system.
Case Study : Delhi’s first Net-Metered Residential 2kWp Solar Rooftop System with BSES Rajadhani
Based on the consumer’s load profile, net-metered solution was the best suited option. He can generate in sunny hours and consume or sell to grid and import power in evenings when he needs it. Balance of his import and export is the only payable.
Project History :
To achieve 2kWp Solar in just 9 Sq mt roof surface, High efficiency SunPower Panels was to be used. Panels were then imported together with other consignment and arrived at site in Aug’14.
Once the Policy was announced in Nov’14 (113th day from receipt of Panels at site), panels were installed and request submitted to BSES. Being first of its kind BSES and customer both took time to progress in application and on 211th Day permission to commission the plant was arranged. 217th Day installation was completed with invertor, BoS and details provided to BSES for acceptance.
Acceptance of the invertor (VDE vs IEC certification) etc. has taken a lot of time involving manufacturer, BSES, CEA, CERC etc. to work together and finally got accepted on 397th day. Agreement between BSES and consumer for net-metering was signed on 419th day and system was started on 422th day in Oct’15.
Solar System :
Generation is recorded in Solar Meter and if load is available it is consumed within the house, if not it is exported to grid. When Solar is not available, power is imported from the grid and balance of Import & Export is the payable units by Consumer to BSES.
Project Cost :
The total project costed about Rs. 2.35 lacs (Approx. Rs. 119/Wp) from concept to commissioning. This is twice the typical commercial rooftop plant >100kWp is built nowadays.
Much contrary to the beliefs the good quality equipment in smaller ratings has very limited choices and costs are very high. Since Modules are not indigenous, this plant is not likely to get any subsidy. The breakup of cost is as below :
The analysis of Solar Generation :
The Solar Generation in past 3 months is max 7 units in a day and it’s 2-3 units/kWp/day as average. Keeping this it predicts a trend to reach a max 1800 units per year much lower to the predicted 3000 units/ year.
The possible reasons which may be attributing to this lower generation:
1. Conversion Equipment efficiency may be lower.
2. Azimuth (5 deg) and lower tilt (18 deg) of panels’ installation due to safety constraints.
3. Panels might have some permanent degradation as it remained exposed but disconnected for a year.
4. The irradiation on the panels may be low then the extrapolation of historical data.
5. Smoggy weather.
Since onsite panels & equipment testing is not feasible, there is no weather recording and data logger at site, it is not possible to conclude on any of the resolution. The cost of improvement is expected to cost more than the generation.
The analysis of Return on investment:
The calculations below predict that the ROI is expected in 13-14 years instead of 8-9 years predicted. The returns don’t beat the simple interest on the capital employed.
The conclusion:
This case study is an eye opener on residential rooftop Solar systems in India proving that the conventional approaches & current policies will never lead to success.
To promote residential rooftop system, the capital subsidy has to be given to each and every project without any limitation on the components selection.
Incentives should also be added for Promotion like Income Tax benefit much similar to AD benefit in commercial cases. The Capital investment in Solar should directly reduce the tax burden.
VAT, Service Tax, GST, Excise, Customs etc. should be kept nil on Solar equipment’s, Promotion of Solar Through bank’s like EMI on other capital goods, certified trained system integrator across are much needed requirements.
