Communication, entertainment, and information are as critical for rural living as they are for urban living. Access to modern communication, information, and entertainment media makes rural lives more productive and comfortable.
Powering Audio-Visual Equipment in Rural Areas
As rural people increasingly demand these services, there is correspondingly rapid growth in demand for audio-visual equipment in off-grid rural areas. Today rural projects, businesses, schools, and a growing number of households make daily use of audio-visual equipment (radios, televisions, videos, mobile phones, etc.).
There is a wide range of energy sources, including renewable energy sources, that can provide power for them. They could be as crucial as a 2-way radio link between a remote clinic and an urban hospital, a computer for a rural NGO office, or a simple radio cassette player used in a household for entertainment.
Audio-visual Considerations: Think About Your Power Requirements Before Purchasing Your Off-Grid Appliances
When powering audio-visual equipment, there are a number of issues that need to be carefully considered in the planning stages. Some of the issues set out in the introductory module are repeated here. Most audio-visual equipment, if selected carefully, can be powered with PV systems in a cost-effective manner.
There are three general categories of audio-visual equipment, which commonly need to be powered in remote areas:
- Educational and Office Equipment: Desktop computers and monitors, laptop computers, modems, slide projectors, overhead projectors, televisions and video recorders and video players (VCRs), cassette players and speakers, etc.
- Communication Equipment: Two-way radios, radiotelephones, phone/fax systems, broadcast radio, etc.
- Entertainment/Sound Equipment: Black and white TVs, color TVs, video players, radio cassettes, public address systems, etc.
Ordinarily, audio-visual equipment is purchased without thinking about the power supply. For off-grid situations, the power supply must be considered at the purchasing and planning stages.
You should answer the following questions before buying:
How many needs will the system supply? Are there only one or many appliances?
Usually, those using audio-visual appliances will require lights in the same place they are based. They may want 2 or more additional appliances where they are based. A household might want lights, a radio, cassette player, and a TV. Or, an office might want a computer, two-way radio, and lights.
It makes sense to design the energy system to meet the energy demand for all of these appliances at the same time, including future additions, if possible.
How many hours are the appliances going to be used each day?
This is critical for the design of the energy system, and factors into the daily energy requirement calculation. You will have to provide this information to the system designer.
What is the power rating and efficiency of each appliance?
When you have to pay for a power system (especially PV or wind), it makes sense to choose equipment that uses as little energy as possible. Most people who buy appliances for on-grid use do not stop to think about the efficiency of their equipment. When moving to, or setting up operations in an off-grid location, this becomes paramount. Table 1 shows typical power use ratings of a number of appliances.
For example, the choice of computer type has great financial implications. The difference could be between a $4000 PV system to power a desktop computer or a $600 PV system to power a laptop.
Are the proposed appliances compatible with each other and with the energy system?
When selecting appliances, you need to make sure that either:
- They are of the same voltage
- The system caters for all of the appliance voltages
For example, a 240VAC video would require an inverter if powered by a 12 DC solar electric system; and that cost should be included in system budgeting. In many cases, it would be easier to purchase a 12VDC color video/TV set, which is widely available.
Avoid a situation where many different appliances with different voltages and power requirements are mixed together. For example, proper planning could avoid the expensive situation where a desktop computer is powered by a diesel genset, a cassette player operates on dry cells, and a lighting system is powered by a lead-acid battery.
Instead, they should all be powered by a single integrated system. Remember that suppliers can help you design a system that best meets your needs.
Table 1: Typical Audio-Visual Appliances and their Power Requirements
|Appliance||Typical power rating
|Typical use per day (hrs)||Voltage rating||Is PV a good choice?
(Typical system size)
|Black and white TV||12-18 W||2-6 hrs||12VDC, or 110/240 VAC||Yes. 20 – 60 Wp|
|Color TV||40-60 W||2-6 hrs||240/110AC or 12VDC||Yes. 80-150 Wp|
|Video||20 – 40 W||1-4 hrs||240/110AC or 12VDC||Yes. Add 20 Wp for ordinary use.|
|Radio-cassette (depending upon speaker output required as with PA system)||5 – 80 W||2 – 12 hrs||6-12VDC||Yes. 5-60 Wp|
|Public Address/PA System
(Amplifier, mixer and speakers)
|50 – 100 W||1 – 6 hrs||12VDC or 110/240 VAC||Yes. 40 Wp or more, depending on size and usage|
|Desktop computer and monitor||400 W||4 – 8 hours||110/240 VAC||Expensive (300 Wp or more). Use hybrid system.|
|Laptop computer||20-40 W||4-8 hours||Yes. 40 Wp|
|Two-way radio||5-10W standby, 40-50W transmitting||0.5-3 hours transmitting, 12 hours standby||Yes, normally 80 – 100 Wp|
|Fax/answering machine||30-60W||continuous||110/240 VAC||Could be (new technology with “sleeper” systems now coming on the market)|
|Slide projector||150 – 300 W||2 4 hrs/week|
|Overhead projector||150 – 300 W||2 4 hrs/week|
Educational and Office Equipment
Computers/Modems/Printers and Peripherals
There are two general types of computers: desktop PCs with monitors and laptops with incorporated monitors.
Laptop computers are extremely efficient, often consuming less than 30 watts of power. Their monitors, CPUs, drives, and modems are incorporated into a unit powered by a single power supply source. They also have a battery that can be used if the power source (PV or genset) goes off-line. Although laptops actually operate at between 9 and 18VDC (depending on the brand), they usually have a power cord and inverter for 110/240 VAC.
12VDC PV or RET systems can be used to power laptops. It is advisable to use a small inverter to step the power up to 110/240 VAC.
Portable PV modules are available that are specially designed to provide 2-4 hours of power for laptops. They can be carried with the laptop during travel (see, for example, Keep It Simple Systems, solar power for portable computers).
NB: Laptops are always preferable in off-grid situations due to their lower energy use.
Desktop computers are expensive to power in remote situations. The monitor and CPU combine to use up to 350-500 Watts of power. However, because their purchase price is generally cheaper than laptops, many field officers end up with desktop computers.
Solar PV may be a viable option if there is only one desktop PC (and few other appliances), especially when the computer is used only for several hours per day (<5 kWh/day energy use).
Gensets (or hybrid power supply with PV or RETs) are probably a better option if there are two or more computers used for more than 4 hours per day, and particularly if there are other appliances in use (>5 kWh/day energy use).
Do not forget to consider CD drives, zip drives, floppy drives, modems, and printers in your energy calculations. You should find out power consumption and input voltage rates before buying if possible. Make sure that their special electronic requirements are met.
Bubble jet printers are normally better choices than laser printers off-grid. Laser printers use much more energy and require special types of inverters (sine wave. Ask your supplier about powering your printer).
Slide projectors are available in both 110/220VAC and 12VDC. Compare the rated wattage of various units before selecting. They use comparatively large amounts of power to run bright, hot bulbs and cooling fans. Normally, slide projectors are used on an occasional basis (i.e., not every day), so their energy use is relatively small.
Overhead projectors are not commonly available in 12VDC. Their power consumption is about the same as slide projectors, but in many places, they are used on a daily basis. Consumption from daily use of projectors will add significant costs to energy systems.
Communication devices are common requirements in rural project offices or missions, and are in increasing use in rural, off-grid households and commercial establishments. They can be inexpensively powered by solar electric power or wind generator systems.
You should carefully estimate the amount of time you will use your communication device to enable proper sizing of the energy system. Care should be taken to make sure that shadows from antennae do not shade solar modules, as this can greatly reduce output.
Two-way radios are the most common communication tool used in missions, police posts, and refugee operations. HF (high frequency) and VHF (very high frequency) radios are both used. Note that radio power consumption is much higher when transmitting than it is when receiving or on stand-by. You will need to calculate carefully how much time is spent transmitting.
Under typical use, most HF radio systems can be powered by 80-100Wp of PV. NB: Suppliers of radios and remote telephone systems should be able to help design power systems for their products.
On-Line telephones (i.e. phones connected to company wires) are powered by the telephone company and do not need a power input from the consumer. However, faxes and answering machines do require power. They should be chosen carefully, as they may use 40-60W on a continual basis (over 24 hours, this is the daily output of 4 or more PV modules). Avoid them if you can.
Satellite and Iridium Phones are efficient and use a minimum of power. Usually, 50 Wp of PV or less will be sufficient to power them.
Cellular phones have lower voltages and contain nicad batteries. Small PV modules (i.e. 1-5 W) can be purchased to charge the batteries inside the phones. Check with PV catalogs.
Radio telephones come in a variety of configurations. Check with the supplier company about power requirements.
Entertainment and Sound Equipment
Televisions and videos are increasingly in demand in rural areas by households, institutions, and commercial groups.
Small 12VDC black and white (B&W) TVs are widely available and well suited to rural household needs. Consuming 12-18W, many can be powered by either AC or DC voltages. Small B&W TVs can be powered by systems sized 30 Wp and above (a 12 Wp module can run one B&W TV for a few hours a day in sunny weather).
Color TVs come in a wide range of sizes. Large 50cm screen units use 120 Watts and above. Smaller units are available that use 60 watts or less. When selecting, be sure to check the power consumption. Most color TVs are rated at 110/240 VAC, but some are available at 12 VDC.
For small requirements, it might be useful to search for the 12VDC type. If you use a 110/240VAC TV with battery system and inverter, be sure that you select the right type of inverter, as some will make the picture fuzzy and add hiss to the sound.
It is important to select a video with the same voltage as the TV (i.e. do not mix a 240VAC video with a 12VDC TV!). Note that combined 12VDC video/color TVs are available, and may be appropriate for small PV systems.
Radio cassettes, radios, and stereos are the most common sources of entertainment for rural people. They also play a vital role in information access for rural people.
Radios commonly use dry cells for power. Rechargeable nicads with small solar modules (i.e. 1-3W) are enough to power most small radios. Small solar modules are still specialty items and should be sourced from catalogs.
Radio cassettes and stereos are more elaborate and consume more power than radios. Radio cassettes use anywhere from 5 Watts up to a hundred. The number of dry cells required (i.e. 2, 4, 6, 8) gives the voltage of the unit, as each cell is equal to 1.5 VDC (6 cells is 9VDC).
You will usually have to buy a DC-DC converter to run radio cassettes from 12VDC systems. Radio cassettes and stereos are usually over-rated in terms of output by 50% or more. Thus, if a unit is rated at 80 watts, it will consume 40 watts or less under normal volume. Consumption increases with increased bass response, and volume control. The size of PV or RET system required to power a stereo will depend on its size and usage.
Public address (PA) systems are required at public service meetings, seminars, and workshops, and at religious services, discos, concerts, wedding parties, sports events, and political campaigns alike.
PA systems are rated at 80 watts and greater, depending on the size of the venue. The rated size of the amplifier will provide an indicator of the system size required. Daily usage in hours must be factored into the sizing. Obviously, a system used daily will require more power than one used occasionally and on weekends.
There are a wide variety of public address systems available, and you can find them in 12VDC or 110/240VAC. Check with your supplier for estimated power usage.
Audio/Visual Energy Options
Audio-visual appliances share a need for electric power. When the appliance is larger than a radio or cassette player, supplying it with power in off-grid areas is often a major challenge. Low-cost PV systems have greatly expanded the variety of equipment that can economically be powered off-grid, but planners still need to be aware of what they are buying beforehand to avoid costly mistakes.
It is common for groups to start operations in an off-grid area with equipment that is inappropriate for the power supply capabilities of, for example, a small PV system. In such cases, they are forced to spend much more on energy supply equipment than they expected. Such situations can be avoided by advance consultation with appliance and energy equipment suppliers.