Final Report Summary - MICRODRY (Microwave Drying for the Rapid Remediation of Flooded Buildings)
Executive Summary:
In excess of 50 million European citizens now live in areas at risk of flooding with business and industry also located in such areas. Equally, the impact of flood events will increase because the magnitude and frequency of floods are likely to increase in the future as a result of climate change i.e. higher rainfall intensities and rising sea levels.
Types of water damage include flooding (natural disaster), pipe bursts and faulty domestic appliances. Water damage accounts for over 60% of buildings insurance claims across the EU. Damage to buildings can range from minor effects on walls, floors, basements and services to serious structural damage along with growth of fungi and bacteria. The major cost of water damage remediation results from the lengthy drying time (up to 8 weeks) required by existing technologies; these costs include alternative accommodation provision, equipment hire and service company labour cost. The delays before a building can revert to normal use also obviously have social consequences.
This consortium has designed and developed a microwave drying system, Microdry, for use in flood remediation operations. The system employs industrial microwave technology in combination with sensor feedback and an intelligent control system to significantly reduce the drying times of flooded buildings while ensuring safety of personnel and equipment in the treatment area and the surrounding environment. Significant improvements are obtained in the drying rates of the different materials. For every 10°C increase in surface temperature, the drying rate for normal concrete improved by 60-70% and by 30-40% for lightweight concrete. The drying rate for clay bricks was improved by up to 230% when drying to 80%ERH. The improvement in drying rate for Thermalite was of the order of 200-300% when drying to 10-30wt%. Wood materials, Oak and Pine, also showed an improvement of the order of 50-80% when dried to 30wt% (near the fibre saturation point).
Project Context and Objectives:
Water damage to buildings affects citizens and businesses across the EU. Types of water damage include flooding (natural disaster), pipe bursts and faulty domestic appliances. Water damage accounts for over 60% of buildings insurance claims across the EU. Damage to buildings can range from minor effects on walls, floors, basements and services to serious structural damage. The major costs of water damage remediation results from the lengthy drying time required by existing technologies; these costs include alternative accommodation provision, equipment hire and service company labour cost.
A major cause of water damage results from flooding due to natural disasters which is likely to increase due to widespread building on floodplains as urban populations rise, increased human intervention in the control and flow of rivers, and climate change. Flooding is a major problem in the European Union causing widespread damage to property, posing a risk to health & safety and causing several social problems such as burglary and severe disruption to daily life for low income families without access to affordable insurance.
After a property has been damaged by water, the speed of drying is key to successful restoration as prolonged periods of moisture lead to structural damage, growth of fungi and bacteria. The chosen method to restore the property influences the speed of drying. There have been few changes to the methods used to dry the majority of flooded buildings for the last 20 years. During times of widespread water damage (such as flooding) equipment availability is restricted due to demand and time elapsed for the equipment to work. Shorter drying times can ensure availability of equipment and enable the drying process to commence as soon as possible after the damage has occurred.
The variation of building materials has a large bearing on the efficacy of drying techniques employed, for example concrete floors can hold additional moisture, and using either heating or dehumidifying techniques, it typically takes on average 1 month for every 2cm of thickness to dry and only modest improvements in drying times are possible from dehumidifiers and conventional heaters due to the small vapour pressure changes offered by such techniques (which acts to drive the evaporation process). Remediation costs average €75,000 per property. The average number of properties flooded each year in Europe is 500,000, leading to total costs of €38billion pa1. The Microdry project will enable our SME supply chain to enter into the water damage remediation equipment market through the sales of a high performance microwave drying system capable of reducing the drying time of flooded buildings by up to 90% compared to conventional methods. The system will heat the moisture within the structure using microwaves, reducing the time required for drying, to allow people and businesses to return to the homes and business sites faster, minimising disruption and financial expense. Heating by microwaves allows deeper penetration into concrete and other materials compared to conventional heating methods and therefore allows:
• A more even temperature distribution within the structure (avoiding over exposure of the surface to high temperatures) and more even drying of the structure
• Improved moisture diffusion from the structure, leading to significant reductions in drying time
We will create a safe, intelligent and automated microwave (MW) drying system. Our technology will use an intelligently controlled microwave emitter and system which is capable of increasing the temperature of the moisture and water within building materials in a controlled manner such that evaporation rates can be increased and drying times reduced. As safety is paramount we will use a series of measures to ensure safe installation, containment of microwave energy and monitoring of the system during operation. This project will develop new State of the Art that will:
• Be powered using an intelligent control unit using:
Project Results:
2.1 WP1
1.1.1 Significant Results
• Six case study materials have been identified: Conventional concrete, Light weight concrete, Oak (hardwood), Pine (softwood), Clay-bricks and Granite.
• Diffusion trials have been carried out for the various materials by soaking them in water. Moisture content at different soak levels has been estimated using mass measurements and baseline moisture measurements using a moisture analyser.
• Complex permittivity has been measured across a range of frequencies for the case study materials at different moisture content levels.
• Drying response of the case study materials has been characterised at different levels of microwave power using small scale samples and a multi-mode microwave oven with mass and temperature sensors. The data has been used to develop a comprehensive Matlab based numerical model of the complete drying process.
• A comprehensive risk and safety evaluation has been undertaken for the final system and a 1 page Microdry Health and Safety Brief has been issued.
• Deliverable report 1.1 has been completed and submitted detailing case study materials and their dielectric loss coefficients.
• Deliverable report 1.2 has been completed and submitted with results obtained from the laboratory trials and numerical simulations of the drying behaviour of the case study materials.
1.1.2 Task T1.1 - Research and categorise case study building materials
Following a detailed study (reported in Deliverable Report 1.1) the following 6 case study materials have been selected:
1. Conventional concrete
2. Light weight concrete
3. Oak (hardwood)
4. Pine (softwood)
5. Clay-bricks
6. Granite
These materials represent the various classes of building materials used across Europe. They also have significantly different moisture uptake and response to microwave treatment. As such, a study of these materials will help establish the boundary conditions for the Microdry system.
1.1.3 Task 1.2 - Characterise Microwave reflection coefficient/ dielectric loss for different materials/ moisture content for a range of frequencies
Samples of the case study materials were soaked in water for different durations to simulate different flood events. A coaxial dielectric probe was then used to estimate the complex permittivity of the various materials. These measurements show a clear correlation between moisture content and dielectric properties. It was also found that timber, LWC and NWC have relatively good microwave absorption properties followed by clay bricks. It was found that moisture uptake in granite is very small resulting in negligible change in dielectric properties. The measured data for wood is consistent with literature values while the data at high moisture levels for the concrete and brick samples is unique to this project. This data will be useful for later modelling exercises.
1.1.4 Task T1.3 - Establish relationship between high frequency signal / moisture content
Basic numerical models were established for the dependence of the microwave heating response upon the dimensions and dielectric properties of a test wall. The models showed that the rise in temperature is proportional to moisture content and incident power density. Moreover, the model also helps estimate the maximum incident power density before microwave leakage beyond the wall exceeds safe limits. The microwave leakage simulation is developed further using 3D modelling in WP2.
1.1.5 Task 1.4 - Characterize drying response of a number of commonly used building materials with different levels of microwave power to establish drying times using numerical simulation
In order to characterise the drying response, a detailed design of experiments was carried out resulting in a total of over 400 samples across brick, concrete (lightweight and conventional) and wood (oak and pine). Detailed mass and thermal imaging measurements were made on every sample before and after soaking and before and after microwave treatment at various time intervals. Some of these results were summarised in D1.2.
These laboratory trials were used to validate the basic models of Task 1.3 and a complex numerical model was developed to study the influence of the temperature in the drying time of the case study building materials. The developed model can provide a solution to very nonlinear and complex phenomena. It also helps increase the understanding of the background issues that govern the physics of drying process. The main conclusion from the modelling is that an increment of about 10oC in the wall temperature reduces the time needed for drying by about 50%.
1.1.6 Task 1.5 - Analysis of risk and safety evaluation for final system
A working party meeting was held in March 2010 and a 1 page Microdry Health and Safety Brief issued. The following measures were agreed:
• Exclusion zone around the emitter (fully automated systems designed to ‘fail safe’ in the event of any mechanical or human error),
• Automated monitoring to ensure no breaches of the exclusion zone occur,
• Monitoring of both temperature and microwave field to detect and avoid thermal runaway, and
• Thorough assessment of the area to be illuminated to ensure no metallic structures can transmit microwaves outside the specified zone.
2.2 WP2
1.2.1 Significant Results
• Operational requirements in terms of microwave output power have been established based upon the modelling carried out in WP1 and further 3D electromagnetic modelling in the present work package.
• A suitable emitter based upon a horn antenna optimised for the Microdry system has been designed and developed. Two different horn antennas have been designed, with 15dBi and 10dBi gain, to study the trade-off between drying rate and leakage beyond the test wall.
• At present, the most efficient high power microwave generators are based on magnetrons. A suitable system using a 2kW magnetron has been sourced from Alter Systems. The microwave supply has a number of incorporated safety sensors and is programmable using an analog reference signal. This allows the control system to set the microwave emission power in order to ensure safe and efficient drying.
• All components were tested before integration into a prototype emitter assembly.
• Deliverable report 2.1 setting out preliminary specifications of microwave emitter system components has been completed and submitted.
• Deliverable Report D2.2 on the build and testing of the prototype Emitter has been completed and submitted.
1.2.2 Task T2.1 - Establish operational requirements in terms of microwave output power
Information from WP1 was used to derive approximate microwave power requirements and verify if a domestic power supply could provide the microwave power needed. The calculated power requirements for all materials are around 2kW of microwave power. A 3kW magnetron power supply is needed to generate this power. A domestic mains ring with a 30A limiter can provide up to 6kW – i.e. it can support two such magnetrons. This margin for expansion justifies the choice of a 2kW magnetron which is significantly cheaper than a 3kW model while allowing for future increments in power as suggested by trials in WP7.
1.2.3 Task T2.2 – Design and develop a suitable emitter solution optimised for the system defined in 2.1
A model was produced of the wave front produced by the microwave emitter in 1) free-space 2) when directed onto the case study building materials identified in Task 1.1. Based on this model a 15dBi horn antenna was chosen as the suitable emitter because it:
1. Radiates only in the intended direction and
2. Is capable of handling the power levels being radiated.
The model has also been extended to estimate fields induced on metallic parts within and on the surface of the wall. The electromagnetic simulation results show that the field strengths induced by a 2kW microwave generator on a nail in a wall 1m away are about 8 times lower than the breakdown voltage of air. If the wall is 2m away from the Microdry unit, the induced fields are about 20 times lower than the breakdown voltage of air. Finally, the model has also been used to estimate leakage levels through test walls of the different materials. The highest leakage levels were observed with the wooden walls, where the microwave leakage exceeds the safe limit of 5mW/cm2, (IEC 60519-6), when the walls fall below 12% moisture content. These levels will be validated as part of the drying trials in WP7.
1.2.4 Task T2.3 – Select appropriate power components for maximum operational efficiency
Based on the power estimates and the antenna modelling, specifications were drawn up for the components of the prototype emitter. Following a survey of components available in the market the following components were chosen for the prototype emitter:
1. Custom-built horn antenna: 15dBi gain with WR340 waveguide flange
2. Alter Systems TI020 Magnetron Head with 3kW SM745G Switching Power Supply: Power Output = 2000W, capable of running off domestic single phase supply, WR340 waveguide flange.
Additionally, a 10dBi horn was also sourced to study the trade-off between drying rate and leakage beyond the test wall. The WR340 flange is a standard flange for 2.45GHz magnetron systems and allows easy replacement of antenna/magnetron in case of damage.
1.2.5 Task T2.4 – Build initial prototype emitter assembly
In this task the components chosen previously were sourced and a working prototype emitter was built for integration as part of WP6 and for undertaking the drying trials planned in work package 7. All microwave components were tested using calibrated RF measurement equipment and found to work as per the specifications laid out in Task 2.3.
The horn antenna was shown to present a very good impedance match to a WR340 waveguide at 2.45GHz (S11 < -20dB). The magnetron was coupled to a test microwave cavity using a WR340 waveguide launcher and a microwave power meter. The power meter showed transmitted power levels above 1.8kW. The power meter was also used to show that the magnetron output power can be reliably varied between 10% and 100% of peak output by varying the anode bias level. This bias level will be connected to the control system for closed-loop control of microwave emissions based upon sensor input.
3.1 Work Package WP3 – Design and Development of Moisture Monitor:
Task 3.1 - Select and develop a suitable feedback device to provide provision of closed loop control of microwave output power:
The Microdry system uses a number of methods to control the microwave output power. These include methods to satisfy safety requirements as well as treatment requirements of the wall. The control methods are
1. Surface temperature measurements from 12 infrared sensors
2. Infrared motion detectors monitoring movement in the treated area
3. Emergency stop switches and safety beacon
4. Thermal fuse within magnetron to prevent damage through overheating
5. Remote control of the system from outside of the treated area through Ethernet connection.
6. 2.45GHz microwave leakage sensors measuring the power transmitted through the wall
7. Moisture detector using 8GHz microwave reflection to estimate treatment requirements
This task also helped identify control system components to enable integration of these feedback sensors.
Task 3.2 Build prototype high frequency feedback system
Two prototypes of an 8GHz microwave moisture sensor were developed. Prototype I sent the initial signal through a directional coupler to a 17dB horn, which also received the reflected signal, which was separated from the initial signal in the directional coupler and then measured. However, limited isolation between the transmitted and received signal made this setup suitable only for short range measurements.
Prototype II uses two 20dB horns, one for sending a strong signal and another one for receiving the weak reflection. The reflected signal is then amplified and measured. Moreover, the polarization of the 8GHz signal is at 90° to the polarization of the 2.45GHz signal in order to minimize influence from the high power 2.45GHz heating radiation. In order to be able to log the measured reflection in synchronization with the scan of the Microdry unit, prototype II was modified to use the Wago PLC in the Microdry unit, instead of an independent data logger, to measure the reflected signal.
Task3.3 - Test and calibration of high frequency feedback system for range of materials and microwave reflection coefficients
In order to optimise available resources, the characterisation of the microwave moisture sensor was combined with the drying trials. Reflectance from the wet walls was measured as a function of time while the samples were dried during the validation experiments. This allows a study of the reflection as a function of both - sample dimensions and drying history of the samples.
Characterisation trials were carried out on the different building materials with an aim to establish a correlation between moisture content and reflected power. While the data collected did indicate a general amplitude variation with moisture level, a consistent and coherent correlation was difficult to establish. Attempts were made to collect reflected phase as well in order to augment the data. However, measurement and analysis of the reflected phase is extremely complex and requires extensive calibration at each test location. This results in the microwave moisture sensor being more complex and time-consuming than conventional moisture measurement techniques. On the other hand, calculated and empirical data from the microwave leakage detectors can be used to develop a power roll-off for walls of the different materials during the drying process. This achieves a purpose similar to moisture measurement and also helps maintain safety of the system.
In view of these factors, despite the considerable development effort put into the microwave moisture sensor, the consortium has agreed to employ conventional moisture sensors in future commercialisation efforts.
Significant Achievements in Work Package 3:
- A feedback system incorporating a number of sensors has been developed to operate the Microdry system safely and efficiently
- Two prototype microwave moisture sensors have been developed for inclusion in the feedback loop so that microwave power output can be controlled by considering moisture within the wall.
- Characterisation data was collected using the microwave moisture sensors for all the building materials considered in the validation trials.
- Deliverable Report 3.1 on design of feedback system completed and submitted in period 1.
- Deliverable Report 3.2 describing the prototype High frequency feedback completed and submitted in period 1.
- An addendum to Deliverable 3.2 detailing design and characterisation of the moisture sensor, has been submitted.
- Work package 3 milestone of Prototype high frequency feedback system has been achieved. A complete closed loop feedback system including moisture measurement by reflected microwaves has been developed and characterised. The system operates well in a controlled environment. However, in view of variability of results in a real flooded environment and the costs of ensuring a controlled environment, the consortium has made a commercial decision to employ conventional moisture sensors in the final Microdry system.
2.3 WP4
1.3.1 Significant Results
• Operational requirements and specifications for the feedback and control systems have been established.
• D2.1 indicates that the power requirements for the microwave sources will be lower than the originally envisaged 14KW. The new estimate allows the power architecture to be simplified using a single supply connection per microwave source.
• An output power management system has been developed which allows the power level to be matched to the requirements of the process.
• A suitable software system has been designed and developed to allow control of the microwave output power for optimal drying.
• A prototype power management and control system has been built and tested.
• Deliverable Report 4.1 on the design of the power management system has been completed and submitted.
• Deliverable Report 4.2 describing the prototype power management and control system has been completed and submitted.
1.3.2 Task T4.1 - Establish operational requirements and specifications for feedback and control system
Given the reduced power requirements identified in D2.1 the hardware complexity of the power control system is substantially reduced. It has been determined that the power control system can be implemented largely in software within the PLC. The feedback system will comprise of the moisture and temperature sensors monitoring the progress of the drying process. Based on the feedback, the software control system will determine and set the correct output level. Additionally, if any of the safety devices are triggered the microwave output will be shut off.
1.3.3 Task T4.2 - Develop an output power management system where the power level is matched to the requirements of the emitter
This task developed a power management system to control the power output from the emitter to maintain steady drying rates considering factors such as variable moisture content in the building materials, temperature and the input power available. The power control system has been implemented within the Wago 750-872 PLC. In order to alleviate the complexity, cost and inefficiencies of power combining stages, individual commercially available power supplies will be used for each microwave source. The power management system will control the overall power consumption of the Microdry system by controlling the output levels of each microwave source.
1.3.4 Task T4.3 - Design, develop suitable software to allow control of the microwave output power for optimal drying
A detailed process control algorithm has been designed to take into account the progress of the drying process as well as inputs from the safety systems to control the microwave output power. Additionally, being mindful of the limited power available, in the final Microdry system the heating of the walls will be carried out in stages. Suitable logic has been developed for these stages to be run for optimal drying without drawing too much power from the mains ring. This includes staggered triggering of multiple emitters and temperature dependent power profiles. Finally, the control system also takes an input from the microwave leakage detector to trigger a roll-off or shutdown of emitted power if the leakage exceeds safe limits.
1.3.5 Task T4.4 – Build prototype power management and control system
A prototype power management and control system was implemented based on the design of the hardware and software aspects in Tasks 4.2 and 4.3. The control system software has been implemented in the native Wago PLC programming language and allows control of the magnetron power supplies through an I/O interface.
1.3.6 Task T4.5 – Test Power management control system
In the field trials, the sensor feedback system will be used to control the output power of the magnetron. In this task the control signals to the magnetron were tested by varying the inputs from the various sensors which form the feedback system. The implement power control algorithm was found to work as expected with the microwave emission power reducing in response to higher temperatures reported by the IR temperature sensors.
1.3.7 Task T4.6 – Develop Remote monitoring system
A highly extensible web server based remote monitoring interface has been developed within the control system. This interface, accessible via Ethernet, enables the operator to monitor the various sensors and control the entire drying process without being in proximity of the Microdry unit. By adding an external wireless router with internet access, stationed outside the treatment area, the control interface can be accessed from any location with internet access.
3.2 Work Package WP5 –Design and Development of Safety and Additional Systems
Task 5.1: Development of the Doppler motion detection system
Various sensors were surveyed to identify a suitable motion detection system that is sensitive enough to detect incursions without causing false alarms. The Gardtec Gardscan MX Passive Infra-Red (PIR) detector has been identified to be the most suitable commercially available system. Four such sensors will be implemented in the first prototype with a range adjustable from 2m - 12m.
During validation trials it was determined that the best location for these sensors is at the point of entry into the treatment area. This location reduces the interference suffered by these sensitive components. An alternate configuration used in the drying trials at Rainbow International is the use of magnetic switches on doors to the treatment area. These switches are more robust and have been used to automate the switching off of the Microdry system in case of inadvertent entry into the treatment area.
Task 5.2: Develop external microwave detection units and local communication methodology
A network of microwave leakage detectors have been developed and will be deployed outside the Microdry usage area to ensure that microwave emission levels outside the boundary stay below the regulatory limit of 5mW/cm2. These detectors are capable of being deployed in power levels of up to 500mW/cm2 and feature a battery life of upwards of 3 months or can be run off a mains supply. The detectors are equipped with an RS232 port to allow wired operation or deployment in a mesh network using Laird AC4868 RF modules operating at 868MHz. Metal shielding and ac power adaptors have been included to make the detectors very robust.
A wireless link was implemented between the microwave detector and the PLC in order to increase the range of the sensor and allow communication without the need for cabling. Laird Technologies AC4486 (868MHz) radio modems were used to implement an RS-232 wireless link between the slave, microwave leakage detector, and the master, PLC. Additional slave leakage detectors can be added to the network without significant re-programming. Interference tests were carried out to verify performance in the presence of high power 2.45GHz signals. It was verified that even in the low power (3mW) mode, communication links could be maintained over 20m through multiple walls.
Task 5.3: Development of the telemetry system
A telemetry module has been developed within the Microdry project to allow the control system to send out short messages reporting progress or alarms to the user. The module communicates with the control system over the RS232 port and sends out messages to the user using a GSM network. The module can be configured for use anywhere in the world where there is a GSM network by simply swapping the SIM card.
- The Microdry prototype control system includes a remote web interface accessible over Ethernet. This web interface highlights and can log any issues arising during the drying process.
- Additionally, a telemetry unit based on a Telit GSM862 module has been developed for integration with the control system.
- Using the telemetry unit the PLC will be able to send simple messages (SMS) of the format “ALARM SYSTEM FAULT” or “ALARM BOUNDARY BROKEN” to the user.
- Moreover progress of the drying process can be reported periodically using a format such as “Moisture xx% Wall Temp xxoC Amb Temp xxoC”.
Task 5.4: Study efficacy of augmentation with venting/ dehumidification systems
This task was used to evaluate the efficacy of the Microdry unit with and without the augmentation systems to establish if there is any enhancement of the Microdry system when used in conjunction with such systems and, more importantly, to verify the improvements due to use of the Microdry system. Trials have shown that when the Microdry unit is used in conjunction with augmentation systems such as a dehumidifier and an air-blower, drying is significantly faster. In order to study the specific impact of the microwaves, rotation of the Microdry unit was disabled. These tests showed a remarkable difference in the drying rates of the portion of the wall subjected to microwaves and the portion that wasn't. For every microwave induced 10°C increase in surface temperature, the drying rate for normal concrete improved by 60-70% and by 30-40% for lightweight concrete. The results show that microwave treatment heats the wall more uniformly to temperatures higher than the ambient temperature. With increase in the wall temperature, the moisture movement is increased and conventional drying systems help complete the job by efficiently removing the moisture, especially in closed unventilated spaces.
Significant Achievements in Work Package 5:
- Infrared motion detectors were chosen for the Microdry system and previously reported in period 1.
- A modular microwave leakage detector has been designed to be capable of deployment as either a high power detector for use inside the treatment area or a low power detector for use outside the treatment area. The detector uses an RS232 communication link to feed into the control system. Metal shielding and ac power adaptors have been included to make the detectors very robust.
- An RS232 wireless master/slave network was developed using 868MHz AC4486 modems from Laird Technologies. The link was found to offer over 20m range through multiple walls and was resistant to interference from the 2.45GHz radiation used for heating. This wireless link can incorporate the telemetry system implemented using the Telit GSM862 module. This module has been tested and can short text updates using SMS.
- Deliverable 5.1 containing test data and summarising the efficacy of augmentation systems was submitted. The report showed that drying is significantly faster when the Microdry unit is used in conjunction with augmentation systems such as a dehumidifier and an air-blower than when either system is used on its own. Moreover, for every microwave induced 10°C increase in surface temperature, the drying rate for normal concrete improved by 60-70% and by 30-40% for lightweight concrete.
- Work package 5 milestone: Prototype remote monitoring and telemetry system has been developed and tested to meet the required performance metrics. The wireless link was found to offer over 20m range through multiple walls and was resistant to interference from the 2.45GHz radiation used for heating. Multiple microwave leakage detectors can be added to the network without the need for significant reprogramming.
3.3 Work Package WP6 – INTEGRATION:
Task T6.1 – Development of integrated system including microwave emitter, feedback system and power management system
An integration plan was developed to ensure easy deployment and transport of the Microdry system. Additionally, a modular approach was adopted very early in the development stage to allow addition/removal of features as highlighted during validation trials. This included the various sensors, horn antenna and software elements. Moreover, all subsystems developed in work packages 2 through 5 were designed with future integration and compatibility in mind.
The Microdry system design is sub-divided into the microwave, sensor, mechanical and power management subsystems that are integrated through a central control system. Modular design allows addition and removal of features as needed while maintaining certain core safety features. The Wago PLC based control system is easily extensible and is broken into a sensor interface and control interface for further modularity and independent location. This allows the sensors to be located in the main treatment area but the control system to be located in an adjacent room with only an Ethernet link between the two sub-systems.
Task T6.2 – Integration of safety features to prevent accidental exposure to microwave energy (proximity sensor, remote control system, safety overrides)
The Microdry unit has been constructed with utmost care to maximise safety and minimise accidental exposure. Safety is ensured by considering both external and inherent factors. External factors include the movement of people, electrical failures and failure of any component of the support sensor system. The inherent factors are those caused by the microwave radiation. While the power of the microwave system has been chosen to limit leakage outside the treated area to safe levels, microwave leakage detectors have been designed and integrated into the system. A number of Microwave detectors will be placed throughout the testing area and outside: at the door, below the testing room and behind the wall being dried. These will be used to trigger a shutdown of the microwave emitter if the measured value exceeds safe limits.
- The Microdry system incorporates PIR sensors to detect motion and microwave detectors to monitor leakage levels outside the treatment area.
- Some safety features are integrated into the magnetron head, such as an arc detector and a thermal fuse to prevent unsafe operation of the microwave subsystem.
- The control system constantly monitors the safety sensors and shuts off the Microdry unit if it detects an alarm or loses communication with one of the sensors.
- Three “Emergency Stop” units are included to allow the operator to switch off all units in case of an emergency.
- The mechanical structure has been designed to eliminate finger traps as far as possible. Where such dangers cannot be eliminated they will be identified in the prototype.
Task T6.3 – Develop power input system to use mains electricity power
The Microdry unit includes a power management subsystem for safe and intelligent power control. The magnetron power supply is a 3kW unit that can be run off a single phase domestic mains supply. The microwave power output is controlled by a central control system that also controls all the external sensors. The control system determines the required microwave output by taking into account information from the ambient and wall temperature sensors. The sensors, stepper motor and the control system are powered through independent power subsystems with a combined power consumption of less than 250W.
- The entire Microdry prototype unit has been designed to run off a single phase domestic mains supply.
- The microwave power output is controlled by the central control system that also controls all the external sensors.
- The power management subsystem is integrated with the safety sensors through the control system. The power management subsystem is implemented within the control system and uses an intelligent algorithm to control the microwave power output.
Task T6.4 – Build of prototype fully integrated system
The prototype Microdry system consists of the following subsystems: Microwave, Sensors, Mechanical, and Power. These subsystems are integrated through a central PLC based control system. The prototype unit has been built to ensure ease of movement and relocation. The Microdry unit can be wheeled into the treatment area, plugged into the mains supply and be ready for use. Once the unit is switched ON all sensors are active. However, microwave emission is only initiated after the operator completes a brief safety check on the remote interface.
The integrated prototype was shipped and commissioned at the premises of IceTec in Reykjavik for validation testing in Work Package 7. During commissioning, the electromagnetic shielding of the system was improved by replacing all direct connections into the control box with connectors containing filters. Additionally, cables were shielded with a thick metallic mesh and the infrared temperature sensors were shielded using hollow aluminium extensions which attenuate the microwave energy. The PIR sensors were disabled for some of the trials because of their extreme sensitivity to interference. In later trials, they were deployed near the point of entry to the treatment area. Additionally, magnetic switches were trialled and found to be suitable for deployment on the doors to the treatment area.
Significant Achievements in Work Package 6:
- All the sub-systems developed in WP2, 3, 4 and 5 were integrated with the control system.
- Sub-system and integrated system performance was tested in conjunction with the development of a set-to-work procedure. This procedure also aids in the training of personnel and the safe setup of the Microdry system. The procedure is accompanied by a comprehensive risk assessment and a safe operating procedure. These will be reviewed following the validation trials in WP7.
- System performance was made more robust by shielding all the sensors from electromagnetic interference. This was achieved by wrapping additional shielding gauze around the sensor cables and eliminating leakage into the control system by adding connectors and grounding to the metallic sensor box.
- Deliverable 6.2 Fully integrated system prototype has been completed and submitted. An addendum detailing the shielding carried out to improve performance in high electromagnetic interference conditions has also been submitted.
- Work package 6 milestone: An integrated microwave drying system with various safety and efficiency features has been developed and used for validation trials as part of work package 7.
3.3 Work Package WP7 – Validation:
Task T7.1 – Test of prototype using a range of common building materials and structures to evaluate system capability
Drying trials have been carried out on 1mx2m test walls built using the case study building materials – concrete, brick and wood. Flood conditions were simulated by storing the materials in a moisture chamber at 20°C and 100% relative humidity before they were tested. These tests were also used to validate the performance of the sensor, control and safety systems. The resulting test data for each material is used to evaluate the suitability of the Microdry system while benchmarking critical performance factors such as drying rates, heating and damage, if any.
It is clear from the measured results that microwave treatment heats the wall more uniformly to temperatures higher than the ambient temperature. This results in three distinct benefits that speed up the overall drying process:
- The surface layer of air close to the wall is at a higher temperature than the ambient temperature and becomes less humid than the ambient relative humidity. The difference between the relative humidity of the air adjacent to the wall and the equivalent relative humidity of the wall surface drives moisture out of the wall so lower surface RH% value accelerates the drying rate.
- Higher vapour pressure of water within the wall (due to higher temperature) strongly increases the transport speed of water within the wall.
- The Microdry system can be used with relatively lower ambient temperatures – thus improving the efficiency of the dehumidifier. A good balance between efficiency of dehumidifier and convective/irradiative losses can be achieved by employing the hot air blower.
Significant improvements were observed in the drying rates of the different materials:
- For every 10°C increase in surface temperature, the drying rate for normal concrete improved by 60-70% and by 30-40% for lightweight concrete.
- The drying rate for clay bricks was improved by up to 230% when drying to 80%ERH. The improvement was 40% when drying to 60%ERH due to the reduced efficiency of microwave drying at the lower moisture levels.
- The improvement in drying rate for Thermalite was of the order of 200-300% when drying to 10-30wt%.
- Wood materials, Oak and Pine, also showed an improvement of the order of 50-80% when dried to 30wt% (near the fibre saturation point). However, it was observed that a more uniform temperature distribution is needed for these materials because they are susceptible to cracking and bending if the drying rate is not uniform.
Moreover, the overall energy consumption in the drying process is reduced due to the reduction in drying times without the need for very high power microwave equipment.
Task T7.2 – System debug and optimisation
The validation trials carried out in task 7.1 were also used to evaluate improvements to the Microdry system from a safety and performance point of view. The test results obtained during testing have been used for further optimization wherever necessary.
Extensive safety tests were carried out by considering leakage beyond the wall being treated and near the points of entry into the treatment room. Leakage was measured using the ETS-Lindgren HI-6005 electric field probe. This probe was used to calibrate the microwave leakage detectors developed in the project which were deployed at various locations around the test area. Additionally, the operator used a commercial hand-held microwave leakage detector to carry out surveys before entering the treatment/control areas.
In terms of microwave leakage, extensive and continual safety tests showed no leakage greater than the permitted safe level of 5mW/cm2 beyond the treatment area except when operated at more than 50% power with nearly-dry wood. In such cases the microwave output was reduced to safe levels through the feedback loop based on input from the microwave leakage detector.
As described in Task 6.4 system performance was made more robust by shielding all the sensors from electromagnetic interference. This was achieved by wrapping additional shielding gauze around the sensor cables and eliminating leakage into the control system by adding connectors and grounding to the metallic sensor box.
Improvements were made to the software control and interface by adding the capability to show a trend plot of measured sensor parameters and making minor changes to the rotation system. Online programming of the control system was enabled and employed for all modifications. This allows the system to be updated remotely over the Ethernet link.
Task T7.3 – Development of operating procedures for commercial processes
Comprehensive set-to-work procedures, risk assessments and safe operating procedures were developed for the safe deployment and operation of the Microdry system. These were periodically reviewed during the validation trials and updated as essential. Recommended safety signs were also highlighted and have been used for the trials at IceTec and Rainbow International. Additionally, feedback from trained operators at the end-users, Rainbow International, was used to improve the Safe Operating Procedures.
Significant Achievements in Work Package 7:
- Following on from the augmentation trials carried out as part of Task 5.4 full scale validation trials were carried out in Task 7.1 using common European building materials. These trials helped establish the boundary conditions for the use of the Microdry system with respect to safety and cost-benefit. Specifically, it was shown that, depending upon the nature of the material, drying rates improved by between 40% and 300% when subjected to microwave treatment. It was also ascertained that the microwave leakage levels beyond the treatment area were always within safe limits (5mW/cm2).
- Extensive and continual safety tests carried out using calibrated equipment showed no leakage greater than the permitted safe level of 5mW/cm2 beyond the treatment area.
- Documentation prepared, as part of work package 6, for safe setup and operation of the Microdry system was reviewed and updated in Task 7.3 in conjunction with the validation trials. Additionally, feedback from trained operators at the end-users, Rainbow International, was used to improve the Safe Operating Procedures.
- Deliverable 7.1 Test report for the prototype system has been completed and submitted. The report shows that significant benefits can be gained from the use of the Microdry system in flood remediation operations. Additionally, it was shown that the system is capable of switching off or reducing the microwave treatment levels based on wall surface temperatures and microwave leakage levels behind the wall.
- Work package 7 milestone: Demonstration of prototype system in ‘wet space’ was successful showing excellent improvements in the drying rates of the case study test walls when subjected to microwave treatment. The improvements were achieved without compromising the safety of the system. More details are available in deliverable report 7.1.
Potential Impact:
This consortium has designed and developed a microwave drying system, Microdry, for use in flood remediation operations. The system employs industrial microwave technology in combination with sensor feedback and an intelligent control system to significantly reduce the drying times of flooded buildings while ensuring safety of personnel and equipment in the treatment area and the surrounding environment. Significant improvements are obtained in the drying rates of the different materials. For every 10°C increase in surface temperature, the drying rate for normal concrete improved by 60-70% and by 30-40% for lightweight concrete. The drying rate for clay bricks was improved by up to 230% when drying to 80%ERH. The improvement in drying rate for Thermalite was of the order of 200-300% when drying to 10-30wt%. Wood materials, Oak and Pine, also showed an improvement of the order of 50-80% when dried to 30wt% (near the fibre saturation point).
Microwave drying system capable of reducing the drying time of flooded buildings by up to 90% compared to conventional methods. The system will heat the moisture within the structure using microwaves, reducing the time required for drying, to allow people and businesses to return to the homes and business sites faster, minimising disruption and financial expense. Heating by microwaves allows deeper penetration into concrete and other materials compared to conventional heating methods and therefore allows:
• A more even temperature distribution within the structure (avoiding over exposure of the surface to high temperatures) and more even drying of the structure.
• Improved moisture diffusion from the structure, leading to significant reductions in drying time (8 weeks reduced to one week).
We will create a safe, intelligent and automated microwave (MW) drying system. Our technology will use an intelligently controlled microwave emitter and system which is capable of increasing the temperature of the moisture and water within building materials in a controlled manner such that evaporation rates can be increased and drying times reduced. As safety is paramount we will use a series of measures to ensure safe installation, containment of microwave energy and monitoring of the system during operation. This project will develop new State of the Art that will:
• Be powered using an intelligent control unit using:
o Externally located microwave detectors with a communication link to the main Microdry unit to allow the surroundings of the treatment area to be monitored for any stray microwave emissions.
o Motion sensors to detect if the area being treated has been compromised and switch off power.
o The Microdry unit’s emissions themselves to further monitor the area for motion using Doppler detectors combined with microwave sensors that are capable of detecting the temperature of the material/ surface being heated to ensure overheating does not occur.
o Adjustable power output for efficient use of power and prevent over heating/ drying of the material.
• Use MW sensors to account for substructure features and the complexity of the field whilst avoiding damage.
• Run using mains electricity whilst monitoring the current drawn and the socket temperature to avoid overheating and overloading of the domestic electricity supply.
The income to each flood remediation company depends on the speed at which they can dry out a flooded building. Faster drying allows more buildings to be treated in a shorter space of time generating a higher return on their equipment costs.
Once the flood water has receded the drying period can be several months, during which time businesses are prevented from normal operations and people need take leave in order to address the problems with their domestic properties. Due to the nature of the damage and the necessary work to dry the property it can take the occupant a significant amount of time to redecorate, leading to lost labour days while completing the clean up operation.
Approximately €6.8 billion is spent on temporary accommodation due to long drying time alone. Based on reduction in drying time alone, Microdry could potentially save EU insurance companies some €850 million and more importantly returning people to their business and homes more quickly
Work has been undertaken to ensure the protection and management of knowledge, and the exploitation and dissemination of the project results. Activities related on generation of a detailed dissemination and exploitation plan; protection and exploitation of knowledge; and the technology transfer and dissemination to target and wider markets.
The public website has been created for both as a Promotion and dissemination through the website’s public area where non-confidential information can be viewed in order to disseminate the projects objectives ahead of formal dissemination events and for partners to be able to view documentation created as a result of any research, meetings, presentations and disseminations events.
An Microdry ‘Image’ has also been created . The draft dissemination and exploitation plan created and submitted as detailed in Deliverable report 6.5 in Period 1 has been further updated
Publishable project materials that will allow effective technology transfer, dissemination and project promotion activities by the project partners, ensuring appropriate Microdry look and feel, with the correct Project Microdry image has been made available. This includes MicroDry Video clip, Project Banner, Project Hand-out, and Project Flyer as detailed in Deliverable 8.1.
List of Websites:
The website is available to the Project Consortium and the Home Page is also available to the General Public. Visit Microdry at http://microdry.pera.com
The Project Manager for the Microdry Project is: Mick Parmar, - The UK Materials Technology Research Institute
Pera Innovation Park, Nottingham Road, Melton Mowbray, Leicestershire, LE13 0PB (UK)
Tel: +44 (0) 1664 501501
Fax: +44 (0) 1664 501423
Email: mick.parmar@uk-matri.com
The Project Coordinator is Alejandro Flores
Space Unit
ERZIA Technologies S.L.
Castelar 3
39004 Santander
Spain
Tel. +34 942 29 13 42
Fax +34 942 29 13 47
Email: alejandro.flores@erzia.com
www.erzia.com
