AdB_AsphalticaPadova_2003

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Research & Development Conference Papers

A.H. de Bondt

GENERATION OF ENERGY VIA ASPHALT PAVEMENT SURFACES

prepared for

Asphaltica Padova

2003

P.O. Box 1 Phone +31 229 547700

1633 ZG Avenhorn Fax +31 229 547701

The Netherlands Internet www.ooms.nl


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Asphaltica Padova - 3 december 2003 - page 1 of 8

Generation of Energy via Asphalt Pavement Surfaces

dr.ir. A.H. de Bondt Ooms Avenhorn Holding bv, the Netherlands ([email protected])

Introduction

Due to their black surface, even in moderate climates such as for example in theNetherlands, bituminous pavements can reach considerable temperatures during summertime. This phenomenon, in combination with the increasing severity of truck loadings, hassometimes caused dramatic rutting problems in recent years.

However, it should be realized that high asphalt temperatures also create opportunities. Aconsortium consisting of several types of companies (Ooms Avenhorn Holding, WTHvloerverwarming and TipSpit) was founded in 1997, in order to develop a methodologywhich is in an efficient way capable of making use of the energy introduced in the pavementby the sun. This methodology called Road Energy Systemsworks in general in its simplestform as follows: in summer, cold water is pumped up from a specific underground storagemedium (in the Netherlands often an aquifer) and transported through pipes in the upperpart of the asphaltic layers. Due to the effect of the sun, the water gets warm. Via anexchanger, this heat is transported into another underground reservoir (the so-called hotone) and stored at this location. In winter, the system operates in the opposite way (thestored heat flows from the hot storage medium to the pavement).

The asphalt-aquifer system described above, only has the potential of cooling the pavementin summer (thereby reducing rutting) and heating the pavement in winter (therebyeliminating icy driving conditions). lt is obvious that a much more cost-effective andenvironmentally friendly way of exploiting the investments for the transportation/storagesystem can be obtained by introducing buildings and heat pumps. This also becausemodern (office) buildings need a lot of (electrical) energy for cooling purposes in summertime; partly due to the better insulation. Figure 1 illustrates the way in which the so-calledasphalt collector can be utilized.

Figure 1 Principle of the Asphalt Collector


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First of all in this paper two important aspects of asphalt/building/aquifer systems will bedescribed in detail; thermal as well as (asphalt) pavement technology aspects.

Thermal Aspects

To enable reliable thermal design of these types of systems, an in-situ testing programmewas carried out in Hoorn, the Netherlands between 1998 and 2001 [1]. lt consisted ofmeasuring temperatures and flows at about 150 locations along different kind of speciallyprepared (instrumented) pavement sections. Figure 2 gives an overview of the location,whereas figure 3 shows typical data from these test sections [2].

Figure 2 Overview of the Prototype Test Site

Figure 3 Typical Example of Measurements (Input and Output)


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Dutch Climatic Conditions

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2,0

0 5 10 15 20 25 30

Inlet Temperature Water [C]

AnnualEnergyOutput[GJ

/m]

Heat

ColdWearing Course

15 mm

35 m m

Wearing Course

15 mm

35 mm

Dutch Climatic Conditions

0

5

10

15

20

25

30

0 5 10 15 20 25 30

Inlet Tempe rature Water [C]

AverageOutputTemp

erature

Water[C]

Heat

Cold

W e a r i n g C o u r s e

1 5 m m

3 5 m m

W e a r i n g C o u r s e

3 5 m m

1 5 m m

The energy (heat as well as cold) which can be generated by an asphalt collector dependson a large number of parameters, such as the input temperature of the fluid which is used asa transport medium, the flow, the depth of the pipes within the pavement structure, thethermal properties of the materials of the pavement structure, etc. By using the data from theHoorn test sections, a computational tool has been developed, which is capable of assessingthe performance of the asphalt collector for other climatic conditions than the Netherlands [2].

Figures 4 till 6 show relationships which can be utilized in the first phase of the design of anenergy concept in which an asphalt collector is applied. Note that these design curves areonly valid for Dutch climatic conditions.

Figure 4 Example of Annual Energy Output Curve (Dutch Climatic Conditions)

Figure 5 Example of Average Output Temperature Curve (Dutch Climatic Conditions)


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Dutch Climatic ConditionsWearing Course 35 mm

0

200

400

600

800

1000

1200

-800 -600 -400 -200 0 200 400 600 800 1000 1200

Capacity [W/m]

HourswithSpecificCapacity

(groupedper50W/m)

Inlet Temperature: 5 C





Figure 6 Example of Distribution Capacity Curve (Dutch Climatic Conditions)

Road Construction Aspects

Since the Hoorn test sections were part of a heavily loaded route for the transport of sandand aggregates, with slowly driving (overloaded) trucks, the situation was ideal to test alsoto what extent the system could be optimized with respect to the laying process and

durability under mechanical loadings. Key factors (targets) in the development phase werethat a) the construction of an asphalt collector should be possible in a short period of time, inorder to keep the possibility that it could also be applied on existing pavements and b) thatone could be sure that the presence of the pipes would have no detrimental effect on thelifetime of the pavement. Via several steps (using several prototypes) the system shown infigure 7 has been found to be the optimum one.

Figure 7 Overview of Final Asphalt Collector System


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In order to make it possible for the system to enter the market, since 1998 several(innovative) actions have been carried out by Ooms Avenhorn Holding:

- a new laboratory test set-up was created to simulate the effect of the asphaltcompaction process on the (plastic) pipe, needed for the pipe selection process

- a three-dimensional grid was developed to fix and protect the pipe during thelaying and compaction of the asphalt mixture

- special grips were made to enable grid testing in the laboratory- optimization of laying techniques and procedures for the pipe as well as the grid

(also near pavement edges, around corners, in curves, etc.)- development of a tool for the estimation of the required cooling equipment for the

system during the laying of the (hot) asphalt mixture- adaption of routine road construction quality control procedures- finite element computations on pavement engineering aspects, see figure 8 [3]- establishing of a pavement design approach for asphalt collector systems- development of a special Sealoflexpolymer modified bitumen which enables to

achieve a high quality asphalt mixture in between the pipes and the grid. Criteria

for the bitumen development were: a reduced viscosity (also to fill the gaps), agood low temperature performance (cracking resistance) and a good hightemperature performance (rutting resistance). The latter was achieved using thezero shear viscosity as a parameter.

- tests on system extension and repair (the latter e.g. in case of traffic accidents)- working on a recycling procedure to ensure that this is possible in future

Figure 8 Finite Element Simulation of Asphalt Collector System

The presence of the collector system in the pavement is an interesting pavementengineering challenge, because the consequences of the introduction of a pipe close to the

surface of a standard (usually applied) pavement structure is that around the pipe highstresses are developed during the passage of a wheel load (see figure 9).


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Figure 9 Stress Concentration in the Asphalt without Special Measures [4]

The way in which this problem has been tackled is that a relatively soft asphaltic mixture isused, which has a high resistance to cracking due to stress concentrations. Furthermore,the presence of the three-dimensional interlocking grid reduces crack growth. The expectedrisk for permanent deformation, when using a softer asphaltic mixture, is taken into accountby the presence of the grid, the cooling generated by the system itself and modification ofthe bitumen by means of polymers. With the latter option, the mixture design can beadapted to the traffic loadings which can be expected (regular trucks, or e.g. aircraft onplatforms).

Besides these pavement engineering aspects, also other issues had to be solved, e.g.:

- investigations into legal aspects (ownership, responsibility, maintenance, etc.)with respect to placing a collector system in a pavement

- inventory of organizational procedures for the exploitation of the energy

All in all, it can be concluded that an easy and quick laying/paving process of an asphaltcollector system has been developed, which enables to place the pipes close to the surfaceof an asphalt pavement, without the disadvantage of stress concentrations induced by thepresence of the holes (the pipes). On top of this, the entire chain from the design of anasphalt collector till the removal of it, has been examined and all problems which have come

across or can be expected to become important in future, have been tackled [5].


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Applications (Implementation Phase)

Since its development, the Road Energy Systems asphalt collector system has beenapplied in several projects in the Netherlands:

- at a complex of different type of buildings in Scharwoude (in a parking lot, amunicipal road, an industrial pavement and an entrance slope to a parkinggarage); this in different phases between 2000 and 2003, in total roughly 2200 m2

- an entrance road to a future industrial zone in Hoorn in 2002; roughly 3500 m2- a parking lot near an office in Dordrecht in 2003; roughly 500 m2- a bridge in Rotterdam in 2003; roughly 10000 m2(see figure 10)

Next Steps in the Implementation Phase

At the Scharwoude site, an extensive monitoring project is going on with the purpose ofproviding a) long-term experience with respect to control strategies, reliability, etc. and b)data on temperatures, flows and energy requirements on all key elements of the total system

(asphalt collector, underground storage reservoir and buildings). The data is utilized to verifya software tool (PIA-RES), which has been developed for the analysis of the interactionbetween the asphalt collector, the underground storage system and the energy demand(heating and cooling) of the buildings.

Figure 10 Asphalt Collector System under Construction on a Bridge in Rotterdam

Once enough long-term experience is available, Ooms Avenhorn Holding will be searchingfor foreign partners to export this technology.


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Conclusion

Asphalt pavements can have a significant contribution in reducing the CO2-emissions whichare produced when heating and cooling buildings. This by making use of their capability tocollect heat and cold in an efficient way during the entire year. By means of an enormousamount of R&D-activities by Ooms Avenhorn Holding, this has become practically applicable.

References

1. de Bondt, A.H.; Jansen, R. and van Rij, H. Test Sections Road Energy SystemsHoorn, 1998 2001 (in Dutch).

2. Loomans, M.; Oversloot, H.; de Bondt, A.H.; Jansen, R. and van Rij, H. Design Toolfor the Thermal Energy Potential of Asphalt Pavements. 8th International IBPSAConference, Eindhoven 2003.

3. van Bijsterveld, W.T. and de Bondt, A.H. Structural Aspects of Pavement Heating andCooling Systems. 3rdInternational Symposium on Finite Elements, Amsterdam 2002.

4. van Bijsterveld, W.T. Energy from Asphalt - Analysis of Structural and Thermal

Aspects. MSc-Thesis, Delft University of Technology, 2000.5. van Bijsterveld, W.T. and de Bondt, A.H. Structural Aspects of Road EnergySystems. Internal Report, Draft 2003.

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AdB_AsphalticaPadova_2003