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Solar Panel Efficiency, Costs and Payback in HDB Homes


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So on this topic of portable solar panels, I find that it is lacking on the internet. There's not much write-up or how-to size and place to teach layman who are interested but don't know what to get and if you can get anything out of it. So here's my attempt to try to explain (note i'm not an electrical engineer, all googled info). Happy to hear feedback or inputs.

 

The story goes when my sis brought a portable solar panel for fun. So i took it and geeked out on it.

Panel Watts = 21W

Output = 3.5A (dual) - don't know if it's two ports total or per port can output 3.5A

Number of panels = 3

Voltage = 5V

Cost = S$50

 

There are a few components that determine if you will actually get the full advertised Watts (important because this determines how much current Amps (how fast) to charge your battery.

1. Type of USB cable you have - seems like the types I have at home can carry around 1.6A (you can test using this app called Ampere https://play.google.com/store/apps/details?id=com.gombosdev.ampere&hl=en_SG though some calculation and stable test is required, like flight mode, turn off background app, then need to add discharging + charging to = how much current from wall socket to device). There are different types of cables, 2A, 3A USB cable, data or without.

2. Battery storage input charge rate, this is tricky because I have a few powerbanks i tested, like the original Xiaomi 10,000mAh says it can accept 2A but in reality when plugged into the solar panel only can draw 1A, so that's twice the number of hours to charge and wasting the available solar power.

3. Placement of the solar panels. It seems like even in the mornings, as long as the sun shines directly on the panel, I'm able to get close to when the sun shines directly above. These months of the year, I have placed the solar panels on top of the air con condenser outside, and tether the clips to the window sill. Am able to get direct sun usually from 12-5pm at max power generation. Also the direction of the panel plays a part, used to hang the panel outside the window but didn't get as much (about 1-2W difference = 0.2-0.4A). Other months of the year, will have to look into hanging it on the corridor (where the sun is). Because it's a portable system, the connectors are not waterproof (though the panels are). I can get trickle charge the rest of the day from 8-9am - 7pm.

 

So the best setup will be to get,

1. 2x USB cable that can support 3A power rates

2. 2x Powerbank that can support close to 3A input charge rates (using 2A as example calculation)

 

5V x 2A = 10W x 2 = 20W system

to charge a 10,000mAh powerbank at 2A, you will need 5hours of direct sunlight

 

Return of Investment (based on 5 hours direct sunlight per day, 1kWh = S$0.20) = 1000Wh / 100Wh (per day) = 10 days to get $0.20

To get $50 = 2500 days = 6.85 years

Carbon footprint saved (every 10 days) = 0.4313 kg CO2/kWh (<-- is this accurate?)

A tree absorbs 11.8kg CO2/year = 0.3232 kg CO2/10 days

 

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The solar panel looks like this, though I'm not sure if it's from this shop.

https://item.taobao.com/item.htm?spm=a230r.1.14.124.7ffb1964Vj2VJk&amp;id=570992748764&amp;ns=1&amp;abbucket=2#detail

The cost of the solar panel itself is about $0.40/W then plus the protective cover, wiring etc to cost additional.

image.png.8b5148c4db4bd13e28efb016eb234864.png

 

Indeed the cost is higher due to the amount of sun I can harvest (only 5 hours a day, if it is on the rooftop, easily twice the amount). I think this is just like an overview rather than a serious system. Because it's not meant for all weather, the connectors are not protected for water. Powerbanks are not the best way to store power because most things at home are not USB based or 5V/2A rates.

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I think the main issue is how do we generate, store and then use electricity. If you have those new glass type balcony or living room that have sun shinning on it for a good 10 hours a day. You could get a return on the solar panel in about 2 years. Using that stored energy seem to be the problem as our houses are built into the grid - like how are you going to power your TV, aircon, fridge from both sources.

 

Average public household monthly consumption = 376kWh/month = 12.5kWh/day (based on 30 days month)

To generate 12500Wh/day = /300Wh /10hours = 4.16 panels = Sharp panel at $310/panel = $1240 (@ $0.20/kWh = 1240/75  = ROI 17months)

Not too sure how to store battery though, definitely need an Inverter to convert the DC to AC output for use.

 

https://www.letsgosolar.com/solar-panels/rankings/affordable/

https://www.ema.gov.sg/cmsmedia/Publications_and_Statistics/Publications/ses/2016/energy-consumption/index.html

 

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I had done solar experiment which I living in the highest floor… if u can get all round sunlight from sunrise to sunset and is return back to power station… yes, u able to save and earn a bit of income in a long run… but all this equipment have life spend too… if u store to battery, u spend more than earn and oso increase carbon of making all this equipment… so I think it is killing the earth faster than saving the earth…

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Just like u driving a car vs taking public transport… public transport will always run daily even u not taking them… so if more ppl taking the same transport than driving the cars… carbon will confirm reduce… just like flushing the toilet using washing clothes water vs freshwater flushing… u save money on water bill and reduce the carbon too of the filter changing frequency reduce…

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Anyone can tell me what is your average usage of water per person per month? My is about $5 per person for water and $10 per person for electricity per month…

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6 minutes ago, Milky69 said:

Anyone can tell me what is your average usage of water per person per month? My is about $5 per person for water and $10 per person for electricity per month…

Studio_20171227_162653.png.fb491887240e9ca45c249b0a0060d875.png

I'm staying in a 2-room HDB flat (1 bedroom+Living Room) with my SO.

My Monthly usage on Water and Electricity are as below:

(Electricity = kWh, Water = CuM)

Oct 2017: 341, Water: 12.4

Dec 2017: 418, Water: 3.3

Feb 2018: 241, Water: 10.7

Apr 2018: 393, Water: 2.5

June 2018: 439, Water: 9.2

July 2018: 371, Water: 10.2

 

Average out, we use about  367kWh electricity and about 8.05CuM water per person, per month.

Electricity is at $0.2215 per kWh (Singapore Powers, cannot buy from Wholesale yet), while water is $1.19+35% tax = $1.6065+$0.78 waterborne fee = $2.3865 per CuM (future raises in water prices have been reported).

My average cost of Electricity per month = $0.2215 x 367 = $81.2905.

My average cost of Water per month will = $2.3865 x 8.05 = $19.211325.

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Of course the main driver for most people would be to be cost efficient. You simply can't profit from it because you can't sell your electricity to anyone in Singapore. However, do consider the amount of CO2 to the environment that you can offset.

 

If you think carefully about public transport, it is actually worse than cars. Look at how many buses after the peak hours are running on less than 20 passengers. Does the passenger need to travel the bus route distance to reach their destination (vs a car point to point). If you take away the COE, car cost is actually more affordable than public transport. Not forgetting how much taxpayers subsidize the public transport fare and still they are losing money.

 

Looking at battery costs, this year, it is at $260/kWh, so an average household will use 12x$260 = $3120 = /$0.20*12 = 1300 days = ROI 3.56 years

Battery lasts about 8-10 years on a daily cycle.

 

As for whether the construction of batteries produces more carbon than pulling from a power plant... I mean, the power plant is not built beside your house, the oil doesn't come with a pipe from the ground, electricity comes in big pipes in the ground which loses power over distance, power plants can't deal with spikes, instead they have to gradually increase power more than demand to deal with it (additional power is lost for good), then there are the pipes to Indo for the natural gas, all have to be refined before it can be used.

 

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1 hour ago, keyboard said:

Looking at battery costs, this year, it is at $260/kWh, so an average household will use 12x$260 = $3120 = /$0.20*12 = 1300 days = ROI 3.56 years

Battery lasts about 8-10 years on a daily cycle. As for whether the construction of batteries produces more carbon than pulling from a power plant...

 

 

Oooo, all these numbers and environmental friendliness are making you very very sexy! :redface:

Edited by Cube3
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Guest Solar Battery Man

Solar technology is 40 years behind where it should be. When the impending dangers of climate change were recognized by scientists in the 1970s, research and development personnel realized that solar and wind power, as well as electric cars, would be important to making sure we don't destroy our planet, and there were indeed some politicians who listened and there was hope on the horizon.

 

Then the US and UK made unfortunate turns to the right in the 1980s, and went totally into the pockets of the fossil fuel industry, and the rest is history. Even worse, a working electric car was developed in the early 1990s as shown in the documentary "Who Killed The Electric Car," before the fossil fuel industry bought the manufacturer, repossessed all of the electric cars, and cut electric car funding.

 

Another horrific blow was the US election of 2000, as Al Gore was a strong advocate for the environment and technology, and even wrote a book about climate change called "Earth In The Balance" in the early 1990s about 15 years before "An Inconvenient Truth." The Paris Accords were finally a step in the right direction, but as we have seen, there are still forces trying very hard to stop progress.

 

The biggest challenge for solar is creating a way to store the energy collected at night and during overcast or rainy days. If things had moved the way they were headed in the 1970s, there would now be solar power plants filled with giant solar batteries with the capability of doing this, but the fossil fuel industry, power companies, and political puppets don't want to lose control over energy distribution.

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Most of the things that make by material that unable to break down in a short term, it will cause environment unfriendly… solar, wind and water flow powered are useful if the power is return to the main source where these storage power plant is already there… if not every household will cause the increase of unfriendly material usage due to additional battery storage build in every household…

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Public transport having less ppl taking cause of the people drive their cars which jam up the expressway during peak hours… one man one car one carbon produced… compare with buses and MRT… many man one car one carbon produced… who kill the earth faster? Electric car is good idea but it only slow down cause the power is still provide by power plant… only the cause of carbon is at one point and not all around… things have to see in a big picture… I take years to learn and find out all these information and match them up…

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On 8/15/2018 at 6:25 PM, Nipoet said:

Studio_20171227_162653.png.fb491887240e9ca45c249b0a0060d875.png

I'm staying in a 2-room HDB flat (1 bedroom+Living Room) with my SO.

My Monthly usage on Water and Electricity are as below:

(Electricity = kWh, Water = CuM)

Oct 2017: 341, Water: 12.4

Dec 2017: 418, Water: 3.3

Feb 2018: 241, Water: 10.7

Apr 2018: 393, Water: 2.5

June 2018: 439, Water: 9.2

July 2018: 371, Water: 10.2

 

Average out, we use about  367kWh electricity and about 8.05CuM water per person, per month.

Electricity is at $0.2215 per kWh (Singapore Powers, cannot buy from Wholesale yet), while water is $1.19+35% tax = $1.6065+$0.78 waterborne fee = $2.3865 per CuM (future raises in water prices have been reported).

My average cost of Electricity per month = $0.2215 x 367 = $81.2905.

My average cost of Water per month will = $2.3865 x 8.05 = $19.211325.

U should be using air-con or computer on some days…

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With the tech now, we should able to have 3 in 1 collection of power… water flow in the pipes… wind blow… solar…

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I really think solar wouldn't have worked out in the past, simply the technology isn't mature (even now I won't consider it mature as the efficiency is only about 10-20ish%). Why current adoption is much higher is due to cost /kWh, perhaps thanks to countries like China who produces a lot a lot of solar panels. But did you know that Wind energy is actually the greatest renewable energy source in the world for many many years already?

 

I'm not sure when you say takes years to learn does that include the latest information you are taking into account. Because in fact, buses are not more efficient than cars. The likelihood of pushing to public transport might be to,

1. recover cost of building public transport - they need a min number to breakeven and yet not able to cope with peak traffic

2. building roads and maintaining roads are very expensive

3. no land to build roads

to name a few. There are always other perspective on why a certain thing is not done another way.

Edited by keyboard
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Guest Solar Battery Man

The reason solar would not have worked out in the past is because the UK and US governments, in particular, stopped funding research and development when they made their rightward turns in the late '70s and early '80s. The fossil fuel and power grid industries killed the possibility of further advances in solar power and electric cars at that time, as they did not want to be put out of business, which is of course financially understandable but still morally reprehensible. The better path for them would have been to fund the research and development themselves and then take control of the new technology, thus keeping the profits, but switching the sources of the money to inventions which are safer for the planet.

 

The technology for solar power would be much more mature now if Jimmy Carter had been re-elected in the US in 1980. The fossil fuel lovers Ronald Reagan and George Bush Sr. took charge instead, removed the solar panels from the White House, and stopped research and development on solar power. The Earth is now at a critical moment, and efforts to improve solar and wind technology, as well as electric cars, must be pushed into overdrive, if we are to have any hope of trying to somewhat mitigate the increasing dangers of climate change. The issue with parts accumulating would also be less of an issue if the power grid industry had funded the solar industry's development and centralized the giant batteries.

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So heard something about US implementing carbon tax and a google find found this. Straits Times also have an article, say 80% is from industries like oil refinering and semi-con. The tax collected will throw back to the company to "upgrade" to better efficient processes. To me, kinda left hand pass to right hand. But then, if you throw away oil industry out of Singapore, the loss of tax money is greater I suppose. So don't hope for renewables energy in the near future. Energy price for HDB homes will increase due to that, just that we can't do anything about it whereas people in other parts of the world are investing/building clean energy. Even China BYD is building so many electrical buses, and Singapore is still testing solar panels in salt water and sea currents. I'm not so sure why we're putting solar panels in the sea instead of off-shore Wind Farms like other countries. Any idea?

 

 

https://www.channelnewsasia.com/news/singapore/5-things-you-need-to-know-about-how-the-carbon-tax-works-9905952

//

SINGAPORE: Starting next year, the Government will impose a carbon tax to reduce greenhouse gas emissions, as part of its commitments under the Paris climate agreement,

Finance Minister Heng Swee Keat said in his Budget speech last year that the tax will create a "price signal" to incentivise industries to reduce emissions.

 

It will also create "new opportunities" in green growth industries such as clean energy, he added, pointing out that revenue from the tax will help to fund measures by industries to reduce emissions.

 

The tax will affect 30 to 40 large emitters, defined as those that emit 25,000 or more tonnes of greenhouse gases annually. The Government is looking at charging between S$10 and S$20 per tonne of greenhouse gas emissions.

The final price will be announced in the Carbon Pricing Bill, which will be introduced in the first quarter of this year.

While the tax will not apply directly to households, Mr Heng expects a "modest" trickle-down effect on consumers. The idea is for power generators to pass on the cost of the carbon tax, experts said.

 

The National Climate Change Secretariat has said that for the average household living in a four-room flat, the tax translates to an increase of S$1.70 to S$3.30 per month in electricity tariffs.

//

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