Smart Home Case study on energy efficien (1)
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
2. 1 no x Gyser
3. 1 no x Room Heater
4. 1 no x Submersible Pump
5. 5 nos x Tuble lights
6. 1 nos x Sandliare
7. 6 nos x Fans
8. 1 no x TV (TFT) with Set-top, DVD etc.
9. 1 no x Computer
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
13. 1 set x misc household electric / electronic gadgets like mobile, radio, sewing m/c, steamer…
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.
Post Shifting to new Home
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 this positive indication that building design has contributed in optimising power consumption next step was to plan
for a Solar Rooftop.
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.
So after this analysis it was concluded to opt for Net-metered solution. Policy was likely to come soon and thus efforts
started in this direction.
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 (113 th 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 211 th Day
permission to commission the plant was arranged. 217 th 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 397 th 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 :
This plant has 6 nos 327Wp SunPower’s Mono-crystalline panels mounted @ 18 deg tilt with 10 deg azimuth facing south
on 5 story building’s lift mummy’s top feeding to 2.5kW Delta’s invertor and then connected to a Solar Meter and then
Net meter (Both meters sealed by BSES).
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.
6. Dust on the panels. Cleaning of panels at that height regularly is a change. The labour cost for each cleaning is
Rs. 100, 2-3 cleaning per month might add 10-20 units (worth Rs.50-100 max?).
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.
Disclaimer : The facts represented in this article is to promote energy efficient buildings and Solar rooftops without any
intentions to defame or harm anyone. Request all to take it in positive spirit and work together for a better planet.
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
2. 1 no x Gyser
3. 1 no x Room Heater
4. 1 no x Submersible Pump
5. 5 nos x Tuble lights
6. 1 nos x Sandliare
7. 6 nos x Fans
8. 1 no x TV (TFT) with Set-top, DVD etc.
9. 1 no x Computer
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
13. 1 set x misc household electric / electronic gadgets like mobile, radio, sewing m/c, steamer…
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.
Post Shifting to new Home
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 this positive indication that building design has contributed in optimising power consumption next step was to plan
for a Solar Rooftop.
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.
So after this analysis it was concluded to opt for Net-metered solution. Policy was likely to come soon and thus efforts
started in this direction.
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 (113 th 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 211 th Day
permission to commission the plant was arranged. 217 th 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 397 th 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 :
This plant has 6 nos 327Wp SunPower’s Mono-crystalline panels mounted @ 18 deg tilt with 10 deg azimuth facing south
on 5 story building’s lift mummy’s top feeding to 2.5kW Delta’s invertor and then connected to a Solar Meter and then
Net meter (Both meters sealed by BSES).
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.
6. Dust on the panels. Cleaning of panels at that height regularly is a change. The labour cost for each cleaning is
Rs. 100, 2-3 cleaning per month might add 10-20 units (worth Rs.50-100 max?).
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.
Disclaimer : The facts represented in this article is to promote energy efficient buildings and Solar rooftops without any
intentions to defame or harm anyone. Request all to take it in positive spirit and work together for a better planet.