1. How much does The NOMADD cost, and what are the spare parts cost ?
Between 3-5c per Watt installed, with very low spare costs. Unit prices are related to the increase in the profitability of panels. Substantial work has been done to model both manual cleaning costs and the effects of cleaning cycle lengths of greater than a single day in the presence of high background soiling rates and dust storm events. We work with the customer to measure and define their unique input variables such as the value of electricity, the cost of cleaning per kW using other methods, and calculate a yearly value-add of the NOMADD system for their project. In almost all cases using inputs that recognize low labor and power prices in the region, NOMADD still provides a net present value of more than $100,000 per megawatt installed.
2. What are the dimensions and weight of the cleaning system?
The system envelope for a 3.2m width array is a box 3.6m x 0.3m x 0.3m. The system weighs 20kg.
3. How is it installed and how does it move through the module surface and array of modules ? Can it be physically moved from one array of modules to others, or do we need a cleaning system per array ?
The NOMADD can be either retrofit-installed or integrated with understructure at the design phase. It runs on patent-pending rails that ensure the system will translate effectively even if the array or rails are poorly installed, with straightness tolerance up to 50 mm out of square over 3 m. This has been verified in the field, with thousands of meters of translation without a single translation malfunction. The rail and cart system has been trialled extensively in outdoor desert conditions and have not shown any signs of wear or unreliability. Mounted to the cart is the main cleaning device, which does not at any time rest weight on the panel surfaces themselves. In this way, wear marks caused by wheels, tank tracks, or other load-bearing translation systems on the panel surface, will not occur. The system is designed to be cost-effective with a single NOMADD unit dedicated to each row. There are a number of reasons for this, the primary one being that all operational labour requirements are avoided. This is an often overlooked necessity of desert cleaning systems, when temperatures can remain at more than 40° during the night, and labour supply is scarce and expensive to maintain and supervise. The second, is that by dedicating one system per row, the dangers of manually moving the system from one road to another, or running out of operational capacity during heavy dust storm periods is completely avoided.
4. How does it physically interact with the panel surface; could it erode or scratch a coated glass surface ?
Several tens of thousands of passes are performed during evaluation with the NOMADD brush system to ensure no damage to panels. Also, the NOMADD is supported on rails at the top and bottom of the array, avoiding any load-bearing contact on the panel surface. The brushes very specially designed, and run after optimising a large number of variables such as feed and speed rate, brush bristle density and pattern, bristle material, length and diameter. The NOMADD patent-pending brush application mechanism carries the brush and allows it to interact with the panel surface at an angle to the direction of motion, and causes the dust to flick rather than grind as it is removed. This enhances the removal if large or small quantities of dust without water.
5. Is manpower needed for the system operation and/or control ?
No manpower is required for the operation of the NOMADD, beyond a single operator in a remote location who can oversee the site from a distance and observe the operational characteristics of each NOMADD device in real-time through remote sensor viewing and network communications.
6. Is there a real time monitoring system giving information about the cleaning progress and system itself (alarms, failures)? How does it communicate with this control unit ?
The electronic system on board is currently being upgraded to allow wireless communication, so key operating characteristics can be observed at all times remotely.
7. What are the components of the system ? What are the spare parts needed ?
The NOMADD is constructed from simply manufactured aluminium components, requiring a minimum of machining and using sections that are standard sizes. Fittings are stainless steel, and the rollers are similar to those found on heavy duty lifting equipment. This makes the NOMADD superstructure and translation structure extremely rugged and durable, with no exposed perishable parts.
8. What are the consumables (parts, brushes etc) and characteristics of the cleaning tools? How often shall they be replaced? Are they industrial parts that can be easily found/purchased when needed?
The brushes are of a special but commonly available proprietary knowledge material. Each brush has 2 bearings, with a coupling at the top and linking it to a motor. Maintenance will be conducted on a yearly cycle, with a two minute removal of the brush/bearing assemblies from the system in the field, by the removal of 4 single bolts. This assembly is then taken to any nearby air-conditioned workshop, where the bearings can be changed out in a 10 min time period. The assembly is then taken back out into the field and reinstalled. Motors are rated to last at least 3 years in the field, the rollers 5 years, and the main electrical system 5 years between changes. This results in an operational expense of a under 3% per year. Most if not all components can be sourced locally or off-the-shelf from major suppliers.
9. What is the operating time of the battery and the charging time ?
The system has several power options, including an onboard panel for recharging. For a half-hour duty cycle, the system requires a 2.5 hour recharge cycle.
10. What is the real cleaning speed (m2/min) ?
On a 3 m width array, travelling at 0.25 m/s, the device will clean 90m2 per minute, and finish its there-and back pass of an entire 200m row in under 30 min.
11. Where is the device stored during the non-operating times ?
At the end of the row off the panels.
12. Is water, compressed air or electricity additionally needed to run the cleaning system?
No. Each NOMADD unit runs completely independently and without any external cables, on-board water supplies or air reservoirs, or any other such highly unreliable operational requirements commonly seen on cleaning systems that have been developed in far less extreme environments.
13) Does the NOMAAD detect, or sense, special environmental conditions, that will stop the cleaning operation?For example, can it be programmed to do periodic cleaning during night hours, to avoid shadowing ?
The NOMADD has a fully up-gradable, on-board, electronic communication and sensing system. Currently, the devices are operating independently, on a timer system, which also has manual override capability. Thus, during customer trials, and product testing, key variables such as brush rotation rate, feed rate, and testing time- frames, can be rapidly altered on the system, via a touch-screen interface.
14. What specifications are needed to install the NOMADD on different array designs?
Ideally, integration of the NOMADD system with an array design occurs at the design phase of the array mounting structure. The system can vary simply be integrated during the design phase with a simple custom bracket that links the track to the mounting structure. Retrofitted options are less desirable, but still very feasible. However given the immature size of the market in Saudi Arabia and the Middle East and region in general, it is anticipated that NOMADD will seek to partner at the early stages of large-scale array deployment to optimize the effectiveness and costs of the installation process. Installation can be undertaken using very cheap and low skilled Labour, and highly accurate tolerances are not required due to the innovative design, which is an essential requirement for any system being deployed in these regions.
15. What are the smallest and largest arrays NOMADD works with?
The NOMADD system is extremely economical for any system ranging from a single 75 kW row, up until any size array, given that one NOMADD is dedicated per row and completely scaleable. Longer rows of up to 100 kW can also be accommodated. The advantages of having a fully automated cleaning solution for 2 to 500 MW Systems, fully scalable and completely modular, is obvious.
16. What is the most problematic kind of residue accumulation to clean with this device? The easiest?
The most difficult residue to clean for any manual or automatic cleaning method, is bird droppings. These adhere chemically to the panel surface, requiring concentrated spot cleaning to remove. New technologies for bird repulsion are being seen at many trade fairs, and this is not anticipated to be a severe problem. The other advantage of having daily cleaning cycles, is that the dust deposits do not have time to stick fast to the panels over several days. Leaving the cleaning cycle for longer periods means dust has more opportunity to chemically bonds to the surface of the panels, leaving watermarks and difficult to clean residues behind.
17. What type of adjustments are needed for maintenance of the device and how often should they be done?
The patent pending brush mounting system has an inbuilt self adjustment process that allows the system to find its optimum gravity-adjusted angle of progress as it cleans. The clamping wheels on the patent pending track and cart assembly have a single screw adjustment that allows for tightening of the system as the wheels wear slightly over several years, keeping the system running snuggly on the rail. No other adjustments are necessary during the operation of the system. Once the height has been adjusted using a simple screw Jack at the point of installation, the system will remain in operational adjustment for the remainder of its lifetime.
18. What is the estimated longevity for the device?
The superstructure of the device is made from aluminium, which has the same lifetime expectancy of any solar panel array mounting structure, which is 20 years or so in the field. The very few, very simple, consumable parts, such as bearings and motors are to be changed on the maintenance cycle mentioned above. The rugged simplicity of the NOMADD is one of its most powerful features. With only three main moving parts, very little is susceptible to short lifespans. We anticipate that the NOMADD will last the lifetime of the array it serves.
19. Is a dry module surface always needed, or the device can operate properly on wet modules? Would there be any advantages?
A dry surface is needed to clean. Wet surfaces turn the dust to a sticky paste, that is only removable from the brush when dry.
20. Does the brush need cleaning?
No. The brush self-cleans at the end of the row by spinning against a static bar, removing any particles that may be trapped in the bristles at the end of the run.
21. How much energy does the system use?
The entire system runs at under 150Watts, which is the rated output of a single panel or two. Therefore, the NOMADD uses the power generated by a single panel out of more than 300, for only 15 minutes of the day, a total of a minute fraction of a percent of the total energy produced.