Lecture 10: Cities and the Idea of Energy Efficiency

my name is David Su I'm a professor at MIT in the department of urban studies and planning and this is another installment or another lecture in my series of lectures on Urban Energy Systems and policy today we're going to talk about the notion of Energy Efficiency the notion of Energy Efficiency or the idea of energy efficiency is something I've worked on for a long time but I think it's worth examining what Energy Efficiency is what Energy Efficiency is not and what it may or may not achieve the materials for today are all in the syllabus

you can link to all of them in the PDF if you have the PDF copies and it's worth I guess starting today's lecture with this kind of profile of Bruno lur he's a called here a post truth philosopher but I actually don't think that it necessarily captures what his work is about uh he was quite influential in the time I was in graduate school and I think quite influential since in terms of talking about how humans interact with the Nate natural world and environment at the time I was in graduate school in the 90s and

the Au a lot of his work was focused on science technology namely how science scientific facts and how Technologies were produced so he writes about highspeed rail he writes about the early internet in France he goes on to write about other topics about how do humans relate to the natural world and so in this magazine profile the New York Times magazine they write in the subtitle he spent decades deconstructing the ways the scientists claim their Authority a lot of his work is about how institutions and systems create kinds of knowledge or create certain cultures so

I would argue that he's not perhaps a postr philosopher as much as one who examines these systems institutions that surround certain Technologies and that's a theme I want to bring forward in this class I think you've probably heard me allude to this a number of times before how we create institutions how we create markets policies a those all shape how Technologies develop it's also relevant this week because Bruno Lor just died actually a few days ago this is this is an obituary in the guardian you can read obituaries in other major newspapers a lot of

newspapers say that he's one of our most one of the most misunderstood French philosophers but his work was inherently interdisplinary does touch on how humans create what we consider to be objective scientific realities but also how that shapes how we see the world and so this is kind of a theme I want to bring forward to talk about what is Energy Efficiency we can take this very abstract definition I kind of came up with this very parown definition that I thought nobody could possibly disagree with it's the efficient provision of Energy Services instead of Simply

focusing on the efficient use of energy I've tried to reposition it a little bit focusing on the services we get from energy and also the provision you know this energy does not come from nowhere it comes from systems so if we kind of break down this paired down definition of Energy Efficiency we'll focus on Services We can question what the meaning of service is itself what is a reasonable expectation of service here in North America or at least where we're having this class this year we expect to have energy fairly abundant and reliable and cheap

we expect to be able to uh access electricity anytime we flick on a switch we expect to be able to GA up our car anytime we need to of course we know that when those systems are disrupted such as in our hurricane as in Hurricane Ian which is Florida's just recovering from now we know service can be disrupted we know Wildfire can disrupt service and so this you know we don't expect it to happen in these quote unquote I guess um what we call disasters or periodic disasters but we also know these things happen fairly

frequently and increasingly frequently in our older grid so we have to ask ourselves for the future as we plan what our systems are going to look like in the future what is a reasonable expectation of service of course we also should recognize that our ideas about what's Energy Services are will vary according to our expectations and norms and institutions those all vary by places by people and by culture if we talk about energy we have to ask ourselves what counts uh for example if we consider renewable energy we consider it renewable because we get essentially

wind and solar energy from larger geophysical forces or from the sun which is essentially an infinite source of energy falling on the earth which also Powers ecosystems but consider where we draw the boundary for what we consider energy we consider uh renewable resources to be essentially infinite because they come from the Sun at the same time we consider fossil fuels to be relatively finite not only the amount that's produced but also of course the amount that the atmosphere can absorb of carbon dioxide or other greous gas emissions but also consider if we draw our boundary

around cities we as I mentioned in the first lecture we have Upstream emissions and we have Downstream emissions consider trash uh trash was originally consumed materials those required energies to manufacture them that's Upstream emissions we consider the place of consumption quite often to be cities and then we consider the downstream missions the energy or the emissions associated with disposing of tra if we Trace through energy in the same way there's obviously embodied emissions Upstream there's the consumption what we consider to be consumption in let's say cities and then there's embodied energy going out with the

track of course it requires energy to get rid of trash also energy can be generated from trash as in waste to energy incinerators so how you account for what pces energy matters and how we think about Energy Efficiency and of course provision uh like I said before energy doesn't come from nowhere it has to be provided by somebody or by some agency we know that provision of energy is not equal to all people we expect that we have access to as much abundant energy at a reasonable price as we want that's clearly not true in

some parts of even North America not everyone has enough money to pay the utility bills and there's many issues raised by provision do we expect people to pay for all their energy we obviously subsidize other activities and other aspects of Life other public goods such as Transportation why don't we subsidize energy we have a system built where rate payers or users pay for exactly how much they use what does that mean for how much they pay for how much we invest or should we invest in the future in other kinds of energy these are all

questions about Energy Efficiency so again this gets back to the question of how do we Define efficiency which brings me to the Elizabeth shove article sign for today which is titled I think quite usefully what is wrong with Energy Efficiency just to summarize some of the critiques of Energy Efficiency in her article uh the first one is that the recognition that Energy Efficiency is not going to meet climate change on its own even if we consider the theoretical limits of Energy Efficiency as one of the other articles also considers we also I think should recognize

that we are unlikely to read the theoretical limit but even the theoretical limit is not going to reduce greenhouse gas emissions completely also there's a question of rebound effects this is an area that's been studied quite a bit in literature it's also called the jbans Paradox after a British Economist who looked at the likely um scarcity or the British Navy running out of coal of course he studies this Paradox and sees that the British Navy then transfers or changes over to oil or its ships and uses more energy than before so it's kind of given

this rebound effect so the idea that if you use more efficiency more efficient technology user expectations rebound and people actually use more energy than before another simple example is do we actually save energy with Energy Efficiency if we have a more efficient car do people feel less guilty or less let's say uh constrained to drive more uh if Energy Efficiency or gas prices are a constraining effect there's also the critique of Energy Efficiency that simply improving the system rather than over overhauling or rethinking the system completely and of course uh the main point of sh's

article which actually references Bruno Lor quite a bit is that when we think about Energy Efficiency we're basically counting some things rather than others this is what Bruno Lor calls purification you basically purify the object of study we focused on energy itself without thinking about all the political or social entanglements of the energy to get there in the first place for example we talk about reducing our oil use we may not be focused necessarily on where the oil comes from as in discussions of energy Independence or energy dependence if we are getting oil from Venezuela

and Nigeria and Iran and Russia as we quite often do in global oil markets we're basically focused on making our use of oil more more efficient without necessarily taking into account some of these other factors obviously discussions of security often take into account the idea of Energy Efficiency as reducing our dependence on foreign sources of oil is a phrase you'll hear quite often and finally the main critique of Energy Efficiency that summarizes some of these other critiques is that it's essentially a status quo uh view of energy it basically frames or bounds the problem in

certain ways it says that we expect to have a certain level of service we may not take into account what our future rebound effects are or we essentially maintaining the status quo by Framing the problem in a certain way rather than radically rethinking the problem maai takes a different approach I'm going through these texts and I want to show you how the texts reflect different viewpoints or rhetorical framings M says in chapter 19 every big effort helps we've established the UK's present lifestyle can't be sustained on its own Renewables so what are our options if

we wish to get off fossil fuels and live sustainably we can balance the energy budget either by reducing demand or increasing Supply or of course by doing both but he skips down to say in the second paragraph have no Illusions to achieve our goal of getting off fossil fuels these reductions in demand and increases Supply must be big so his emphasis is that we have to do big things that Energy Efficiency should basically reflect this sense which is what matters is the total impact on the problem of energies climate and if you had to characterize

it as an equation simply impact equals the volume of the problem times the change so as he says if everyone does a little we only achieve a little we need big changes in demand and Supply but if we make changes we have to apply those changes to large volumes or the entirety of the problem from the col Allwood papers the 2010 papers you see that these equation a couple times there the potential for saving energy there's the scale of energy flow and it's multiply times the target the difference between the target efficiency and the current

efficiency this fundamentally reflects a different view of Energy Efficiency it matters what how efficient we can get compared to our current level of efficiency so what matters is the potential for Energy savings measured versus current efficiency the Delta essentially depends on this bracketed term the difference between Target efficiency and current efficiency this is a very different view because as Colin all would point out and I'll highlight later in one of the tables that our current use of energy is only about 10 or 11% of the energy the primary energy we consume is actually harvested or

used as final services so as they argue if we can increase our Energy Efficiency we can drastically reduce our use of primary energy or greenhouse gas missions if you look at how they characterize the problem they also say upfront in one of their papers the reasons for using energy more efficiently are clear and then they go down to say there's this Kai identity which is essentially a product of four dve s population per capita wealth energy use intensity which is energy per unit of wealth and carbon intensity which is CO2 per unit of energy and

they go right to say the first two drivers are socioeconomic and are diff difficult to limit in practice getting back to the Bruno Lor view or Elizabeth shub's uh critique of Energy Efficiency we have to critique whether or not these first two drivers are in fact difficult to limit in practice but also when we often say that climate change is a Tech is no longer a technical problem it's a social and political problem we have to question whether or not we can simply take these first two drivers and leave them off the table they spend

most of the time their two papers usefully I think focused on the third and fourth drivers which are technical options which are require energy we used more efficiently and the decarbonization of energy supplies something we've talked a lot about this class but what I'm trying to reemphasize in this class and the reason why I started off by talking about Bruno Lor Elizabeth shove is that we cannot avoid the entanglement of some of these technical issues with social political context and we have to address the soci and economic drivers of energy consumption namely per capita wealth

and per capita energy use in wealthy countries of course they do go on to say that significant socioeconomic barriers also limit the uptake of new efficient designs these include Market imperfections um such as a lack of adequate information and financing higher perceived costs and differential benefits to the owner and user you'll recognize many of these factors including behavioral barriers such as consumer Trends and habits you'll recognize many of these factors are things we identified in previous readings such as the reading by bloomstein Ed Al 1980 as I said in a previous lecture I te that

article every year because all those barriers still exist there's still barriers that we need to overcome but let's get into the meat of their analysis if only because I think they do some useful kind of defining in some ways chunking the problem breaking down the problem into a more practicable set of problems they make this distinction between conversion devices and path of systems they they classify things as energy sources we essentially transform fuels there's some fuel loss in going to refined fuels and electricity for example we go from petroleum to gasoline there's some fuel loss

if we go from coal we can't necessarily use coal in our homes but we can use electricity as we know we lose uh generate we need lose energy to generation distribution and then this goes all the way through to end use conversion what we ultimately want is a set of services let's say we want light in our homes that light in our homes requires electricity so we have to go through the set of losses to get to the endus conversion the end use conversion converts electricity into light and as they say in their article once

things have converted to this end use it's very hard to harvest them again in other words there's some fin service that we want there's some useful energy that goes into that final service but there's a whole series of losses the fuel loss the generation loss generation distribution loss conversion losses and system losses and that's the total losses and they distinguish the final Service as the thing we want and passive systems are essentially systems that do not transform energy again they receive energy at the end they're essentially the nodes at the end of the system another

way to look at energy use is that we have some dist IAL level of energy use we may have a lower hopefully level of current energy use though as I've shown you before current energy use is probably higher than it was historically but the point they want to make is that we have potential to realize Energy Efficiency we have our current level of energy use there's some level of reduction in energy use which is economic in other words it would actually save money or is cost effective to save using energy by let's say deploying new

technologies or policies having said that our economic potential for reduction here about 40% is lower than our technical potential because theoretically we could reduce our energy use by 55% it looks like here if we app applied every possible technology but the difference between Technical and E economic potential is that some things are economically cost effective some things are technologically possible but not yet economically cost effective so that's the difference between these two lines and of course our theoretical potential is a theoretical calculation of how much how these systems could possibly work most efficiently to reduce

their energy consumption completely and so these three distinctions economic technical theoretical potential are something you'll see quite often in Energy Efficiency we also have to question necessarily how these potentials are calculated economic potential is obviously defined in terms of a certain set of market conditions now technical potential is based on a certain set of technologies that exist now and theoretical poten is how we calculate the potential but obviously a new technology or different set of Demands might actually reduce energy consumption just as much as these potentials having said that again you'll see these different definitions

of potential used quite often this is from the doe Energy Efficiency potential studies catalog you'll see they draw a different way technical potential is one Circle this is how much we could reduce energy use technically economic potential is a subset of that achievable potential is smaller still because that's considered uh let's say what's socially achievable or politically achievable which is not the same thing as economically potential uh sorry economically realizable and then achievable and then finally program potential there's a skepticism even from the Department of energy about how effective social or government programs can be

the program potential is smaller than the technical economic or theoretically achievable potential for any given policy technology or Market but they do a useful catalog I guess showing studies at the utility level showing that there's studies that uh e economic and achievable electric electricity savings are between 1 and 1.5% they show that the utility performance is here looks like maybe averaging around 0.5 to 1% there's a higher achievable potential and there's a higher economic potential especially out here at the end you can see they categorize 36 38 and 50 studies they also emphasize in this

catalog that most studies focus on certain sectors they focus on residential Industrial and Commercial sectors they do much less focus on agriculture distribution irrigation and Street lighting which brings us back to our sank diagram of the US economy in 2021 here's our four major sectors here residential commercial industrial you'll notice in that previous diagram they don't show Transportation because we obviously have many ways to make Transportation more efficient but it's essentially considered somewhat different partly because it's outside the jurisdiction of utilities uh we know we directly fuel our vehicles we pump gasoline we think of

that as essentially a different system than our system for Energy Efficiency for residential commercial industrial which is largely governed by utility companies what's useful I think about the colon allward papers is a lot of diagrams that show how things connect for example they show that we have three possible energy sources here on the left oil gas and coal we have three conversion Technologies petrol engines diesel engines and electric motors we have three modes of transportation cars buses and trains and we have a final service that we want to get which is passenger transport the key

thing about this kind of horizontal slice through these vers various Technologies is that some fuel sources or energy sources can only connect to certain conversion devices which connect to certain vehicles for example oil can only produce petrol or diesel we know how we have car Bus and Train versions that use uh petrol or diesel to get passenger transport but if we want to use an electric motor we can only in this uh paper get our electricity from gas and coal sources and we can have to Electrify our cars buses and trains of course it's also

worth thinking about what this chain leaves out it obviously doesn't include something simple like walking you know ebikes or micr Mobility might use electric motors but walking is not something that's counted as a energy source it may fulfill our need for passenger transport and actually may fulfill other needs like let's say increased psychological benefit or increased Health but it's not necessarily captured in how we how we measure these things there's that often uh quoted saying you can't manage what you don't measure this paper these papers are all about measuring certain things and thinking about how

to make them more efficient of course when you measure certain certain things you're not counting other things I think it's attributed to Einstein but it's not necessarily clear if you said it he said you know not everything that can be counted counts and not everything that counts can be counted it's not necess what he said but it's a famous quote attributed to him this is the point of Energy Efficiency also we need to count certain things but we also need to Value some things that can't necessarily be counted if you look at some of the

vertical slices though there's some very useful kind of back of the envelope figures for you to look at we have the total amount of energy use from our energy source about the majority of it is used is more than half of it is used in direct fuel use about 40% of it looks to be used electricity and a very small portion is used actually is heat directly the energy sources are overwhelmingly oil and coal this is 2010 so may be superseded gas is probably higher Renewables are probably higher biomass and nuclear are probably roughly the

same in terms of conversion devices the overwhelmingly used conversion devices for transforming energy are diesel engines electric heaters electric motors and biomass burners and gas burners if you look at the passive systems appliances heated and cooled space steam systems and driven systems dominate our path of systems you can see if we break down our 475 exit jeels of energy buildings and factories are quite High vehicles are actually relatively low but of course all these things mix in to get all our final Services we need Vehicles we need buildings we need factories all mixed together so

if you look at the breakdown of final Services you can see they try to classify how we use our energy thermal comfort and subsidence are relatively high but structure Freight transport and passenger transport are still relatively high amounts of energy because they consume materials because they consume embodied energy as well as direct fuel use so one thing to point out the S diagram and the all paper is that some of these things are shown as slows but through each of these vertical slices you can't necessarily Trace energy all the way through for example if you

go from oil oil can only be used in diesel engines and petrol engines and oil burners so we can kind of account for all this direct fuel use but you know we we use some portion of oil some portion of gas coal nuclear renewable to generate electricity but as you start to move through through these vertical slies it gets harder and harder to account for where these flows go directly for example let's take trucks we go from diesel engines and petrol engines they may map to some extent to cars and trucks but you can see

these flows don't quite line up because across the vertical slices is very hard to account for how many Diesel and how many petrol trucks we have having said that we also know some portion of our trucks planes and ships and trains go into Freight transport they categorize these in various ways how do we categorize Truck transport versus car for passenger transport we know in the United States SUVs are classified as trucks which makes them ex exempt from previous efficiency standards so the point is as you go across these vertical SLI in this particular sanki diagram

you can't always Trace all the flows in the same way that you can in the previous s diagrams we looked at you can see that there's a few gaps in between some of these flows because where electric heat go it goes to a lot of these different systems not necessarily just a heating and cooling space but it may let's say go to Industrial uses having said that we should also look at exactly what they're trying to measure in this paper they make a very clear well they make a series of distinctions between xgy energy and

entropy they quote this Rosen in denser paper from 2008 saying that xgy is a measure of the usefulness or value or quality of an energy form this is defined using thermodynamic principles as the maximum amount of work which can be produced by a system or a flow of matter or energy as it comes to equilibrium with a reference environment and the reason why they make this distinction is because I've said before and also maai writes in his book that there's high grade forms of energy and low grade forms of energy and this intrinsic distinction between

these is entropy for example electricity or mechanical work is the kind of energy that can be uh captured quite easily and recaptured and can also be used for many different things but if you try to heat up a space once you put heat energy into a room it's very hard to recapture that energy then make a distinction can the first electricity or mechanical work is a high graded form of energy and maai calls heat a low-g graded form of energy they make a distinction here by XG saying XG is how much output work can be

captured for the maximum theoretical work that can be captured here's their definition in their papers they say XG efficiency is based on the first and second laws of their Dynamics they use it because they want to provide an equitable measure of conversion efficiency they Define it as mechanical work is mechanical work like electricity can be captured and recaptured quite easily you put into a storage system whether not it's physical or mechanical or chemical can quite often recapture a very large portion of the energy that's not the same thing for a heat battery let's say you

put as I said last week heat into a hot water heater you can store the energy for a long time but it's very hard to take the the heat energy out of the water and recapture for future use or converting it back to let's say electricity or fuel so the reason why uh we look at this col all paper this is actually more like a traditional sank diagram because they actually are much uh they find it easier I think in this paper to measure exactly what the theoretical efficiency limits are they can trace exactly where

the energy sources go because they're not going into different services or different categories of services they Define things more clearly as come from energy sources to direct fuel use to conversion devices they don't have the same vertical slice as the other diagram does and you can see quite clearly in this paper exactly where our energy goes to we start with 475 exit Jews this is global energy demand in 2005 it's probably much higher almost 20 years later but the point is that we only get to about 11% of the total energy is converted into useful

energy namely in the forms of motion heat and cooling light and sound the other 89% we lose to combustion heat exchange oxidation mixing as we transfer heat we lose energy through heat exchange exhaust heat losses and electrical resistance and friction fision this is not to say that they say the theoretical limit is recovering the 89% of Energy Efficiency or energy that's lost having said that we know that we have existing Technologies and systems all these various losses are because of conversion losses the Technologies we have the systems we have convert energy in certain ways into

certain kinds of end uses that we want like light and heat and motion and all those conversion Technologies may be inefficient what the point of this paper these two papers are is that how theoretically efficient could we be they argue that we could be 89% more efficient 89% efficient more efficient would reduce our primary energy use quite a bit and reduce our uh climate change problems also so if you look at how they Define Energy Efficiency they have a quality Factor exergy efficiency the key column to look at here I think is the right hand

side you can look at exactly how efficient are various our various Technologies are for Upstream conversion you can see that electricity generation from oil is relatively efficient actually but much less efficient than fuel Transformations such as preparing direct fuel use or renewable energy resources you can see that oil biomass gas coal and nuclear are much less exergy efficient than renewable or fuel Transformations combining heat and power and heat are also relatively low in terms of their exergy transformation the other thing to notice here is that this kind of quality Factor gets at the idea of

how easily you can convert the energy to xrg and so they put in 100% basically as a plug here it basically accounts for let's say fuel losses or transformation losses and you can see that nuclear Renewables and fuel transformation ations such as direct fuel use are all relatively efficient if only because um Renewables and nuclear power Ed electricity electricity is relatively little as lost in terms of transmission compared to other types of energy fuel transformation is considered to be relative efficient because it's going to be produced as a direct fuel this is only measuring the

efficiency of the Upstream conversion not necessarily the end use down the road which we'll see in this uh next actually table this table shows the exg efficiency of end use conversion devices you can see across the board all of our end uses for motion for heat and for other services are all relatively low all devices convert about 25% of the possible theoretical maximum xrg uh and you can see that's true for almost all of our different Technologies diesel petrol aircraft engines oil burners by biomass brunners and so on one point I always make to engineers

in this class is that if you look at these two tables and the thany diagrams if you're working on these technologies that should hopefully be motivating because you improve one of these Technologies a little bit that technology if that technology can be scaled and adopted widely they can have a huge impact on our total use efficient use of energy if we look at the kind of compound efficiency which takes into account fuel transformation electricity generation and use device conversion again for some actually uh these uh electricity generation does not factor into like the aircraft engines

or coil coal burners they put 100% of the plug here but the key point is you multiply these factors together and to get a compound efficiency so we started out with a very efficient fuel transformation in direct fuel use as in aircraft engines diesel engines and petrol engines but then we exhaust a lot of the energy out because you have to we have to burn the fuel directly a lot of heat goes out the tailpipe or the back of the engine so we actually get fairly low compound efficiencies again across all the converion devices where

we get final Services you can see that the overall average is quite low we have an overall average of average 11% of actual final energy use or final services from the original primary energy going in and so we can take this thinking further this is a the report by Griffith at Al called rewiring America argues that we can have basically a highly electrified decarbonized US Energy sector basically providing all the same services that the US economy current currently provides and argues that we have massive efficiencies in electrification they actually Trace all the energy use through

all the US government reports they can find they identify places where some of the sanki diagram they find either misleading or duplicative because we're actually using fossil fuels they argue that there's some large por about 8% of the energy economy is misleading accounting of existing primary energy if we eliminate fossil fuels we'll get rid of this 8% if we uh we have current losses in residential commercial and the industrial sector because we use fossil fuels if we Electrify these things they'll eliminate basically another looks like about 15% or 16% of energy use if you Electrify

Vehicles they eliminate another 10% electricity use and you can see what they're trying to do is they're getting from the 97 or so quads the US consumed 100 quads and they're trying to increase the percentage of Energy Services at the end Energy Services increasing to 27% and trying to get rid of what they call with quotes waste they argue that some of these waste can be captured through electrication they also do this as in a super stanky diagram I encourage you if you have the PDF to click on this interactive link what was quite useful

about this interactive diagram is you can click on any of the final Services we desire and it'll show you where all the energy comes from the in the U in its history or path the reason why this is really useful is if you think about efficiency we have a set of final surfaces here that we demand at the right we have a set of primary energy sources going on the left if you can reduce consumption on this right hand side you eliminate all the Upstream happening and crucially you eliminate all the previous inefficiencies or losses

in other words if you reduce consumption let's say 1% here you are going to reduce much more than 1% of primary energy use on the left because all the efficiency gains by simply not demanding the final service in the end so this is again why we focus on consumption in this class I want you to think of efficiency as percolating through the whole system if we reduce our consumption or demand how much efficiency doesn't lead to upstream and this brings me back just to this set of final Services we desire passing through transport freay transport

structures suance like Food hygiene and thermal Comfort communication illumination what I want you to think about is if we make these things more efficient either in our conversion devices or in our demand or use of them for example we know about a third of all food in developed countries is thrown away if we reduce our demand for food by being less wasteful how much would we reduce Upstream both in terms of our vehicles factories buildings But ultimately the direct fuel use and motion that actually went into producing a third of food that's wasted we also

know that uh have we could have different demands for theral Comfort based on the calculation we did in class last week if we simply wore a sweater or simply had lowered the degree on our thermostats by one lowered our thermostats by one degree we know that we' actually reduce quite a bit of energy use that goes into thermal Comfort one of the largest categories of energy use so what we're going to think through in class uh on Thursday is I want you to think of yourself as a member of team Heat or motion or other

and we're going to ask ourselves these questions in groups how much energy or Greenhouse Gap missions could theoretically be saved for your team which single technology Improvement for your team this can be a technology in terms of fuel conversion or electricity generation or end use conversion would achieve the greatest production of energy and greenhouse gas emissions what reduction in primary energy could your team achieve with a 20% reduction in final Services how could you achieve a 50% reduction in primary energy and which technology would you try not try to improve or why I'd just like

you to think through these old chain of Technologies systems and demands thank you very much and I'll see you in class soon