Feasibility of solar electricity in Sri Lanka

By Srilal Miththapala & Suranga Karavita

An overview of the state of Solar PV installation in the Sri Lankan hotel industry was carried out recently by the SWITCH-Asia Greening Sri Lanka Hotels programme project team. While doing this study, the project team also analysed the impact of the proposed electricity increases on domestic Solar PV installations as well. A ready reckoner feasibility chart for evaluating financial feasibility of Solar PV installations for residences was also prepared. The following paper discusses these aspects.

Introduction

Of late, there has been much discussion about the generation of electricity from solar energy. This is usually called solar photovoltaic generation (Solar PV), where an array of solar cells, typically mounted on the roof of a building, will capture the solar energy and transform it to electrical energy.

In a conventional or standalone system, the solar electricity has to be stored, since usage (demand) does not always coincide with supply (generation). Hence, in a typical installation, electricity is generated in the form of direct current (DC) and usually stored in batteries. The size of such battery banks required will depend on the size of the installation and the days for which the system can operate on battery power alone, with no input from other generation sources.

In addition, the system requires an inverter to convert the electricity stored in the battery in the form of direct current (DC), to alternate current (AC) at a higher voltage, to be compatible with the downstream installation. The cost of a battery bank can be as much as a Solar PV panel for a well-designed system, which can provide power for several days when the Solar PV is not generating electricity. Batteries are still in the development stage and they are prone to premature failure. So, it is common that in Solar PV installations with a battery bank, some of the batteries have to be replaced before the specified lifetime.

Cost of installation

The high cost of Solar PV panels and the large amount of batteries required for storage resulted in the cost of such installations being prohibitively high and not feasible for installation as alternate energy sources.


With rapidly increasing electricity rates, reduction in price of Solar PV panels and acceptance by the Ceylon Electricity Board (CEB) to trade electricity units with the grid, Solar PV installations are at present becoming more financially attractive.

‘Trading’ of electricity

This ‘trading’ of electricity units, recently allowed by the CEB, is referred to as net metering or grid tie. This is where an electricity consumer is able to generate electricity at the consumer’s own premises, using any form of alternate energy source and can then synchronize the electricity thus produced with the CEB system and ‘export’ it to the CEB.


The consumer is not paid for this ‘exported’ electricity but is given credit (in kWh), which is set off against his normal electricity consumption off the grid. There will be metering for consumption as well for export of energy to the CEB network.

Each month, consumption and export of energy will be compared. If the export is more than the consumption, credit is given (in kWh). If consumption is higher than export, the consumer is charged for net amount of consumption (consumption - export).

This is effectively a ‘win-win’ situation for both the consumer and the electricity service provider (the CEB or LECO). The consumer benefits by being able to export the electricity he generates without having to store it, thereby reducing the need and the cost for a storage battery bank.

From the CEB’s/LECO’s point of view, there is some form of electricity demand reduction from the grid, since the consumer is now producing some quantum of electrical energy.


At present, the cost of investing in a grid tie Solar PV is around Rs.350,000 per kW and the cost of investing in a conventional Solar PV system is around Rs.700,000.
Solar PV installation in hotel industry

In spite of grid tie options being available, the reduction in cost of Solar PV panels and increased cost of electricity, Solar PV for larger industrial applications is still not financially attractive, due to the long pay back periods of around 15 years for a grid tied system and around 30 years for standalone systems.

Hence, from the surveys and studies carried out by the SWITCH-Asia Greening Sri Lanka Hotels programme, it has been found that Solar PV installation in hotels is still few and far between. In fact, from the 350 odd hotels working with the Greening Hotels programme, there are only three hotels, which have some form of Solar PV installations.

Ulagalla Resort

This 80 roomed resort hotel in Anuradhapura has been the trailblazer in taking a bold step in installing the largest Solar PV system in a hotel so far. It has a bank of Solar PV panels covering 900 sqms, generating 120 KW of electrical energy, which amounts to about 40 percent of the hotel’s total electrical demand.

The system operates on a net metering platform and cost about Rs.125 million for the entire installation, which was done with the commissioning of the hotel in 2010. While certainly the hotel has taken a bold and pioneering step in having such a large Solar PV installation, payback periods are still quite high.

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However, the hotel has been able to market this unique installation to give it a strong identity as a hotel which embraces good sustainable consumption practices.

Jetwing Sea and Jetwing Blue

When the former Jetwing Seashell Hotel was refurbished and relaunched as Jetwing Sea, a self-contained (inclusive of battery bank) Solar PV was installed for one wing of the guest rooms in the hotel. The installation cost was about Rs.12 million in 2010 and generates approximately 15 kW.

Former Jetwing Blue Oceanic was also refurbished and relaunched in the same year as Jetwing Blue and a Solar PV system, similar to Jetwing Sea was installed of capacity 20 kW, at a cost of Rs.16 million.

More than being a financial consideration, here again, it has become a unique selling proposition (USP) and a powerful marketing tool. The hotel proudly advertises itself that most of its rooms’ electrical energy is powered by the sun and each room has an indicator to show when the room is powered by solar (green light) and when it is powered by the mains, during low sunlight periods (red light).

Hence, other than for selective marketing and differentiating propositions, currently, larger Solar PV installations, either grid tied or standalone systems do not seem to be that viable in large scale hotel applications.

Solar PV for residences

However, with the rapid increase in electricity rates for residential buildings which consume higher loads, grid tie Solar PV installations are becoming a very much more feasible option.

Provided adequate roof area or space on the ground is available, any residence utilizing more than 300 units of electricity (kWh) per month, with the grid tie Solar PV installation at current cost and new electricity rates (which are being proposed), will pay back in just about less than six years.

The project has developed a ready reckoner, which gives a quick approximate indication of the financial feasibility of a Solar PV installation for residences.

It is evident from the table below, which shows the co-relation of payback periods for Solar PV installations and units consumed, it is evident that the moment a domestic consumer exceeds the lower thresholds of consumption of around 250 units, the effective electricity charges increase exponentially, bringing the payback period rapidly down to seven years and less.

(Srilal Miththapala, an Electrical Engineer by profession and a senior tourism professional and Suranga Karavita, a Mechanical Engineer, are Project Director and Industry Technical Services Manager of EU SWITCH-ASIA Programme Greening Sri Lanka Hotels project implemented by Ceylon Chamber of Commerce respectively)
http://www.dailymirror.lk/business/features/27390-feasibility-of-solar-electricity-in-sri-lanka-.html

Good Article...but can any electrical expert give me a clarification regarding the last comparison chart...

* The first section shows as " Units consumption- kw " then at solar section same line shows as " solar panel size"
is the given size of solar panel produce the kw mentioned on first section..?

ex
consumption Kw 30 = solar panel of 0.25kw...?
consumption Kw 180 = solar panel of 1.50kw...?

Also do our residential Electricity bills are calculated as 01 Unit = to a 1 kw ???

Solar panels are sized in watt peak (Wp), meaning the amount of power it generates during an hour of peak sunlight. The amount of power it can produce in a day is calculated by multiplying the panel or solar array (many panels coupled together) size x approx. 3.5-5 hrs of peak sunlight per day (that can vary from place to place i.e. in the hill country it can reduce to about 2 hours). The above table has calculated it at 4 hours of peak sunlight. For example, a 250Wp solar panel will produce 250 x 4 = 1,000 Watt Hours per day. A 1kW (kilo watt) array will produce approx. 4kW hours of power per day or 120kW per 30 day month

I think it is a very good idea. There are some advantages in this investment.
1) if there are power cuts and fuel shortages there will be no major impact
2) Life after retirement will be less of a financial burden
3) CEB prices will continue to increase since we are more on thermal power.

Wy not lkr. 500K now when you can?

@ Rocky ref: item 1)
If the system is a grid-connected one without a battery bank to store the power (which is usually the case as the power generated will be fed directly to the national grid), then you cannot use the power generated from this system for use during a power cut. If the requirement is to use the generated power as a back-up source, then you need battery banks and the cost will double.

@WWDNF.

Thanks, what will be the cost for a fully fledged solar panel system with a battery life of 2 years?
Any members who have installations could you kindly share your experience with us before investment?

Thanks,

The cost will depend on your usage (i.e. how many watts of power do you use on an average day). The higher the wattage, the higher the cost of the system. You can use the table given in the Switch-Asia article above to get a rough idea on cost (double it if you want a battery bank). However, I must caution you on the choice of batteries. Any company supplying automotive batteries for solar systems should not be touched. The ideal battery for solar is a deep-cycle battery which very few offer. These are a bit costly but they can have a warranty of between 3-5 years. Also, be selective on the choice of solar panels being offered. Some of the cheaper ones use B-grade (or lower grade) solar cells which will not last the 25years warranty on rated power (i.e. the rated power of the panel should not drop below 85% during the warranty period). Go for good quality panels from reputed companies (Kyocera, BP, Sharp, etc.)

@WWDNF

Thanks chum.
I am seriously going for a 25 year life Batt. Cell
We will be sunk if any Air Liners run their planes off the CPC and CEB charges us for it!

RIO wrote:
Also do our residential Electricity bills are calculated as 01 Unit = to a 1 kw ???

1 Unit = 1000 Watt hour = 1KwHr

1000 Watts used in 1 hour = 1 Unit

If we light 100W bulb for 10 hours we consume 1 Unit

If we light 4 60W bulbs for 5 hours each day we consume 36 Units per month.

By using 1200 W electric Iron for 20 minutes ( 2/3 on and 1/3 off)
we consume about 1/4 Units.
For 1 month (25 days), we consume about 7 units.

If you use 1 60W pedestal/table fan overnight (8pm-5am) , 0.6 units per day and 18 Units per month.
Normally avr 2 fans used by each household ( if no A/C) . = 36 Units per month

Refrigerators and Ar conditioners are the main culprits for high electricity bill.

For the 600 W small sized fridge , 24 hrs x 15% on 85% off cycles , consumes 2 Units per day + at least .5 Unit for door openings and motor start.
i.e 2.5x 30 = min 75 Units per month.

Thanks a lot for your kind help...WWDNF & Chinwi..

exactly my Unit usage per month is around 190 [residential]

The beauty of solar systems is that they are modular. You can increase generation capacity as and when you wish, simply by adding more panels!!! Given that the net-metering scheme does NOT pay you for the units that you produce (they simply set off the units you consume from the grid against the units that your solar system produces and feeds the grid). If you produce less than what you consume, you are billed for the excess, but, if you produce more than what you consume, the additional units simply accumulate to your credit. As such, if you are going for a grid-connected system, you should size it so that the amount of units that you produce through your system is slightly lower than what you consume.

@ Rio, if your average usage is 190 units per month, you should ideally install a 1.5kWp system to get the most out of your capital outlay even though the payback is 8+ years (unless you plan to increase your usage and go for a larger system straight away).

Chinwi wrote:

RIO wrote:
Also do our residential Electricity bills are calculated as 01 Unit = to a 1 kw ???

1 Unit = 1000 Watt hour = 1KwHr

1000 Watts used in 1 hour = 1 Unit

If we light 100W bulb for 10 hours we consume 1 Unit

If we light 4 60W bulbs for 5 hours each day we consume 36 Units per month.

By using 1200 W electric Iron for 20 minutes ( 2/3 on and 1/3 off)
we consume about 1/4 Units.
For 1 month (25 days), we consume about 7 units.

If you use 1 60W pedestal/table fan overnight (8pm-5am) , 0.6 units per day and 18 Units per month.
Normally avr 2 fans used by each household ( if no A/C) . = 36 Units per month

Refrigerators and Ar conditioners are the main culprits for high electricity bill.

For the 600 W small sized fridge , 24 hrs x 15% on 85% off cycles , consumes 2 Units per day + at least .5 Unit for door openings and motor start.
i.e 2.5x 30 = min 75 Units per month.

Chinwi, how the scenario would change using CFL or LED bulbs?

We know that 11W CFL = abt 60W normal bulb then when it comes to LED, the same wattage but I think the best thing is the Low Amperage LED consumes..

Any such calculations valid for CFL & LED usage?

WWDNF wrote:The cost will depend on your usage (i.e. how many watts of power do you use on an average day). The higher the wattage, the higher the cost of the system. You can use the table given in the Switch-Asia article above to get a rough idea on cost (double it if you want a battery bank). However, I must caution you on the choice of batteries. Any company supplying automotive batteries for solar systems should not be touched. The ideal battery for solar is a deep-cycle battery which very few offer. These are a bit costly but they can have a warranty of between 3-5 years. Also, be selective on the choice of solar panels being offered. Some of the cheaper ones use B-grade (or lower grade) solar cells which will not last the 25years warranty on rated power (i.e. the rated power of the panel should not drop below 85% during the warranty period). Go for good quality panels from reputed companies (Kyocera, BP, Sharp, etc.)

Abt this battery thing.. U think using car batteries not worthy or useless?

Where to find deep-cycle battery in SL?

Smallville wrote:Chinwi, how the scenario would change using CFL or LED bulbs?

We know that 11W CFL = abt 60W normal bulb then when it comes to LED, the same wattage but I think the best thing is the Low Amperage LED consumes..

Any such calculations valid for CFL & LED usage?

Wattage considered was real usage. - Valid for filament type bulbs.
If you use LED consumption is very much less. When 10W LED gives 60W light, we have to consider 10W as the consumption.

At the moment I rarely used normal bulbs: Fixed only at almost-never used points.
Somehow, fans eat what we save in these hot days.

@Small:
Car batteries have a high failure rate if used for solar (even with a very good quality charge controller). Some of the more reputed solar companies offer deep cycle batteries in Sri Lanka (maybe they will not carry stocks but they can surely get it down for you).

The main issue is the cost of replacement of failed batteries. Imagine if you have to replace batteries every 2 years ? That will be 50% additional capital infusion every 2 years.

You are better off supplying the grid direct and saving on the added expense of batteries for using the system as a back-up power source.

If you really need some back up power to light up some areas during a power failure, you can still have a separate solar panel with a battery/charge controller and connect 1 DC light (CFL/LED) in each area you need lit up. A 25Wp panel with a 35Ah battery can light up to 5 x 5W CFL or LED bulbs for approx. 3 hours per night. If a lesser number of bulbs are used, then you can use the others for a longer number of hours